Radiographic image detection device and method for operating the same

ABSTRACT

In an AED operation of detecting irradiation start of X-rays, a control unit of an electronic cassette selectively outputs the analog voltage signal from a part of the charge amplifiers including a detection CA connected to the detection channel of a detection pixel for irradiation start detection among the plurality of CAs connected to the MUX, to the ADC, causes the ADC to perform only the AD conversion process for the analog voltage signal selectively output from the multiplexer, and reduces the number of pulses NPU_A per unit time in a clock signal defining an operation timing of the ADC compared to that in the image reading operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No.PCT/JP2018/024252 filed on 26 Jun. 2018, which claims priority under 35U.S.C § 119(a) to Japanese Patent Applications No. 2017-126222 filed on28 Jun. 2017 and No. 2018-028298 filed on 20 Feb. 2018. The aboveapplication is hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a radiographic image detection deviceand a method for operating the same.

2. Description of the Related Art

In the medical field, diagnosis based on a radiographic image detectedby a radiographic image detection device is actively performed. Theradiographic image detection device includes a sensor panel and acircuit unit. In the sensor panel, a plurality of pixels that aresensitive to radiation which has been emitted from a radiationgeneration apparatus and transmitted through a subject (a patient) andaccumulate charge are two-dimensionally arranged. The radiographic imagedetection device having the sensor panel is also called a flat paneldetector (FPD). The circuit unit is provided with a signal processingcircuit that converts charge accumulated in the pixels of the sensorpanel into a digital signal and outputs the digital signal as aradiographic image.

The radiographic image detection devices are divided into a stationarytype which is fixed to an imaging table installed in an imaging room anda portable type in which, for example, a sensor panel is accommodated ina portable housing. The portable radiographic image detection device iscalled an electronic cassette. The electronic cassettes are divided intoa wired type that is supplied with power from a commercial power sourcethrough a cable and a wireless type that is supplied with power from abattery provided in a housing.

A switching element for selecting a pixel from which charge is read,such as a thin film transistor (TFT), is connected to each pixel. In thesensor panel, gate lines for driving the TFTs in units of rows of pixelsand signal lines for reading charge from each pixel to a signalprocessing circuit are provided so as to intersect each other. That is,the gate lines extend in the row direction of the pixels and arearranged at predetermined pitches in the column direction of the pixels.In contrast, the signal lines extend in the column direction of thepixels and are arranged at predetermined pitches in the row direction ofthe pixels.

The signal processing circuit includes, for example, a charge amplifier(hereinafter, referred to as a CA), a multiplexer (hereinafter, referredto as a MUX), and an analog-to-digital (AD) converter (hereinafter,referred to as an ADC). The CA is provided for each signal line and isconnected to one end of the signal line. The CA outputs an analogvoltage signal corresponding to charge flowing from the pixel throughthe signal line. A plurality of CAs are connected to input terminals ofthe MUX and one ADC is connected to an output terminal. The MUXsequentially selects the analog voltage signals from the plurality ofCAs connected to the input terminals and outputs the selected analogvoltage signal to the ADC. The ADC performs an AD conversion process ofconverting the analog voltage signal from the MUX into the digitalsignal corresponding to the voltage value thereof.

In a case in which radiation is emitted, charge corresponding to thedose of the incident radiation is accumulated in each pixel. Since theradiation transmitted through the subject is attenuated according to thetransmittance of the subject, the charge indicating the imageinformation of the subject is accumulated in each pixel. The signalprocessing circuit reads the charge indicating the image information ofthe subject from the sensor panel, converts the charge into the digitalsignal, and outputs the digital signal as the radiographic imagecorresponding to one screen for diagnosis.

WO02012/008229A (corresponding to US2013/0140467A1) discloses aradiographic image detection device in which a sensor panel has 2880rows of pixels and 2304 columns of pixels and a signal processingcircuit has nine MUXs and nine ADCs. In WO2012/008229A, when aradiographic image corresponding to one screen is read from the sensorpanel, the signal processing circuit performs the following imagereading operation. That is, whenever gate pulses are sequentiallyapplied to the gate lines corresponding to 2880 rows to sequentiallyturn on the rows of TFTs one by one, the charge of each of the pixels inone row in which the TFT has been turned on flows simultaneously to thesignal line corresponding to each column. Then, the charge of each ofthe pixels in one row is read to each CA connected to each of the signallines corresponding to 2304 columns and is then accumulated therein.Since the numbers of MUXs and ADCs are nine respectively, the number ofcolumns of pixels that one block formed by one MUX and one ADC is incharge of is 256 (=2304/9). Nine blocks operate in parallel at the sametiming. Each MUX sequentially selects the analog voltage signals from256 CAs connected to the MUX and outputs the selected analog voltagesignal to each ADC. Each ADC sequentially converts the analog voltagesignal from each MUX into a digital signal and outputs the digitalsignal. The output of a digital signal corresponding to one rowcorresponds to the reading of an image corresponding to one row. In acase in which the reading of an image corresponding to one row ends, thesame operation is repeated to read the next image. The image readingoperation corresponding to one row is repeated 2880 times correspondingto 2880 rows and the radiographic image corresponding to one screen isoutput.

The radiographic image detection device disclosed in WO2012/008229A hasan auto exposure detection (hereinafter, referred to as AED) function ofdetecting the start of the emission of radiation using the sensor panel.Specifically, the radiographic image detection device repeatedlyperforms the operation of reading the charge of the pixel as the digitalsignal from before start of the emission of radiation, similarly to theimage reading operation. Hereafter, a series of operations whichrepeatedly performs the operation of converting the charge of the pixelinto the digital signal and reading the digital signal and determineswhether the emission of radiation has started on the basis of thedigital signal from before the start of the emission of radiation inorder to detect the start of the emission of radiation is referred to asan AED operation in order to distinguish the operation from the imagereading operation.

In a case in which the emission of radiation has started, the amount ofcharge generated in the pixel increases as compared to before the startof the emission of radiation. In WO02012/008229A, in the AED operation,similarly to the image reading operation, the read digital signal iscompared with a preset irradiation start determination threshold valueand it is determined that the emission of radiation has started in acase in which the digital signal is greater than the irradiation startdetermination threshold value. In a case in which it is determined thatthe emission of radiation has started, a pixel charge accumulationoperation of accumulating charge in the pixel is performed whileradiation is being emitted and then the image reading operation isperformed. The AED function makes it possible for the sensor panel tostart the pixel charge accumulation operation in synchronization withthe radiation emission start timing even in a case in which a timingsignal indicating the radiation emission start timing is notcommunicated between the radiographic image detection device and theradiation generation apparatus, for example, for the reason that theradiographic image detection device and the radiation generationapparatus are produced by different manufacturers.

In the AED operation disclosed in WO2012/008229A, nine MUXs and ADCseach of which is in charge of 256 columns of pixels operate in parallelat the same timing to read charge from all of the columns. This point isthe same as that in the image reading operation.

SUMMARY OF THE INVENTION

The image reading operation ends in a case in which it reads aradiographic image corresponding to one screen once. In contrast, theAED operation is continued from before the start of the emission ofradiation until the emission of radiation starts in order to wait forthe start of the emission of radiation whose timing is indefinite. Forexample, the image reading operation ends on the order of severalhundreds of milliseconds. In contrast, the AED operation is continuedfor a period of several seconds to several tens of seconds until anoperator presses an irradiation switch for instructing the start of theemission of radiation after setting radiation emission conditions in theradiation generation apparatus.

In WO2012/008229A, while the AED operation is continued, the signalprocessing circuit repeats the same operation as the image readingoperation that reads the charge from the pixels in all of the columns.Therefore, there is a problem that power consumption is very high forthe period of the AED operation having a longer operation time than theimage reading operation. In particular, in a case in which theradiographic image detection device is an electronic cassette driven bya battery and has high power consumption, since a battery having alimited charging capacity is used, the battery needs be frequentlycharged. Therefore, imaging efficiency is reduced.

An object of the invention is to provide a radiographic image detectiondevice that can reduce the power consumption of a signal processingcircuit in an irradiation start detection operation of detecting thestart of the emission of radiation and a method for operating theradiographic image detection device.

In order to solve the above described problems, there is provided aradiographic image detection device comprising a sensor panel in whichpixels that are sensitive to radiation which has been emitted from aradiation generation apparatus and transmitted through a subject andaccumulate charge are two-dimensionally arranged and a plurality ofsignal lines for reading the charge are arranged, a signal processingcircuit that reads an analog voltage signal corresponding to the chargefrom the pixel through the signal line to perform signal processing, aplurality of charge amplifiers that are included in the signalprocessing circuit and each of which is provided for each signal line,is connected to one end of the signal line, and converts the charge fromthe pixel into the analog voltage signal, a multiplexer that is includedin the signal processing circuit, has a plurality of input terminals towhich the plurality of charge amplifiers are respectively connected,sequentially selects the analog voltage signals from the plurality ofcharge amplifiers, and outputs the selected analog voltage signal, an ADconverter that is included in the signal processing circuit, isconnected to a stage behind the multiplexer, and performs an ADconversion process of converting the analog voltage signal output fromthe multiplexer into a digital signal corresponding to a voltage value,and a control unit that controls the signal processing circuit such thatan irradiation start detection operation and an image reading operationare performed, in which the irradiation start detection operation readsthe charge through a detection channel which is the signal lineconnected to a preset detection pixel among the pixels from before startof the emission of the radiation and detects the start of the emissionof the radiation on the basis of the digital signal corresponding to theread charge, the image reading operation reads the charge from the pixelthrough the signal line after a pixel charge accumulation period forwhich the charge is accumulated in the pixel elapses after the start ofthe emission of the radiation and outputs a radiographic image which isindicated by the digital signal corresponding to the read charge and isprovided for diagnosis, and in the irradiation start detectionoperation, the control unit selectively outputs the analog voltagesignal from a part of the charge amplifiers including a detection chargeamplifier that is the charge amplifier connected to the detectionchannel among the plurality of charge amplifiers connected to themultiplexer, to the AD converter, the control unit causes the ADconverter to perform only the AD conversion process for the analogvoltage signal selectively output from the multiplexer, the control unitfurther reduces the number of pulses per unit time in a clock signaldefining an operation timing of the AD converter compared to that in theimage reading operation, and in the irradiation start detectionoperation, in a case where power supplied to the charge amplifier duringthe image reading operation is normal power, the control unit furtherdrives at least one of the part of charge amplifiers in a low powerstate in which power lower than the normal power and greater than 0 issupplied.

It is preferable that the multiplexer has a function of selecting theanalog voltage signal from the part of the charge amplifiers among theplurality of charge amplifiers connected thereto.

It is preferable that the radiographic image detection device furthercomprises a first path through which the analog voltage signal from thecharge amplifier is output to the AD converter via the multiplexer, asecond path through which the analog voltage signal from the chargeamplifier is output to the AD converter without passing through themultiplexer, and a switch that selectively switches between the firstpath and the second path, and in which the control unit controls theswitch to select the second path during the irradiation start detectionoperation.

It is preferable that in the irradiation start detection operation, thecontrol unit causes at least one of non-selected charge amplifiers otherthan the part of the charge amplifiers among the plurality of chargeamplifiers connected to the multiplexer to be in a power saving state inwhich the supply power is lower than the normal power.

It is preferable that the power saving state is a low power state inwhich power lower than the normal power and greater than 0 is supplied.Alternatively, it is preferable that the power saving state is apower-off state in which the supply of power is stopped.

It is preferable that the control unit causes all of the non-selectedcharge amplifiers to be in the power saving state.

It is preferable that the radiographic image detection device furthercomprises a first path through which the charge is input to the chargeamplifier, a second path through which the charge is output to themultiplexer without passing through the charge amplifier, and a switchthat selectively switches between the first path and the second path, inwhich the control unit controls the switch to select the second path forthe non-selected charge amplifier in the power saving state.

It is preferable that in a case in which the power saving state is apower-off state in which the supply of power is stopped, the controlunit applies a bias voltage for stabilizing a potential of an inputstage to the non-selected charge amplifier in the power-off state.

It is preferable that a plurality of blocks each of which includes onemultiplexer to which at least one of the detection charge amplifiers isconnected and one AD converter connected to a stage behind the onemultiplexer are comprised, in which the control unit has a function ofswitching a power supply state of the block between a first state inwhich first power is supplied and a second state in which second powerlower than the first power per unit time is supplied, and periodicallyswitches the power supply state of at least one of the plurality ofblocks during the irradiation start detection operation.

It is preferable that in a case where the number of blocks whose powersupply state is periodically switched is two or more, the control unitshifts a switching timing of the power supply state of at least two ofthe two or more blocks.

It is preferable that the two or more blocks are divided into groups,and the control unit shifts the switching timing of the power supplystate for each group. In this case, it is preferable that at least oneblock is disposed between two blocks belonging to the same group.

It is preferable that the control unit shifts the switching timing ofthe power supply state of all of the two or more blocks.

It is preferable that the control unit causes at least one of the blocksincluding the multiplexer to which the part of charge amplifiers is notconnected to be in the second state at all the times among the pluralityof blocks during the irradiation start detection operation.

It is preferable that the block is provided for each area that is formedby the pixels connected to a plurality of the adjacent signal lines. Itis preferable that plurality of the adjacent blocks that are in chargeof the areas adjacent to each other are mounted on the same chip, and aplurality of the chips are provided.

It is preferable that the control unit switches the power supply stateof the block in units of the blocks that are in charge of the areas orin units of the chips.

It is preferable that the detection pixel is a dedicated pixel which isspecialized for the irradiation start detection operation.

It is preferable that a temperature drift correction unit that correctsa temperature drift of the digital signal which is generated by a biasin a temperature distribution in the signal processing circuit due tothe switching of the power supply state of the block.

It is preferable that the radiographic image detection device is anelectronic cassette that is configured by accommodating the sensor paneland the signal processing circuit in a portable housing and is suppliedwith power from a battery provided in the housing.

There is provided a method for operating a radiographic image detectiondevice comprising a sensor panel in which pixels that are sensitive toradiation which has been emitted from a radiation generation apparatusand transmitted through a subject and accumulate charge aretwo-dimensionally arranged and a plurality of signal lines for readingthe charge are arranged, a signal processing circuit that reads ananalog voltage signal corresponding to the charge from the pixel throughthe signal line to perform signal processing, a plurality of chargeamplifiers that are included in the signal processing circuit and eachof which is provided for each signal line, is connected to one end ofthe signal line, and converts the charge from the pixel into the analogvoltage signal, a multiplexer that is included in the signal processingcircuit, has a plurality of input terminals to which the plurality ofcharge amplifiers are respectively connected, sequentially selects theanalog voltage signals from the plurality of charge amplifiers, andoutputs the selected analog voltage signal, an AD converter that isincluded in the signal processing circuit, is connected to a stagebehind the multiplexer, and performs an AD conversion process ofconverting the analog voltage signal output from the multiplexer into adigital signal corresponding to a voltage value, and a control unit thatcontrols the signal processing circuit such that an irradiation startdetection operation and an image reading operation are performed, themethod comprising an irradiation start detection step of performing anirradiation start detection operation that reads the charge through adetection channel which is the signal line connected to a presetdetection pixel among the pixels from before start of the emission ofthe radiation and detects the start of the emission of the radiation onthe basis of the digital signal corresponding to the read charge, and animage reading step of performing an image reading operation that readsthe charge from the pixel through the signal line after a pixel chargeaccumulation period for which the charge is accumulated in the pixelelapses from the start of the emission of the radiation and outputs aradiographic image which is indicated by the digital signalcorresponding to the read charge and is provided for diagnosis, in whichin the irradiation start detection step, the analog voltage signal froma part of the charge amplifiers including a detection charge amplifierthat is the charge amplifier connected to the detection channel amongthe plurality of charge amplifiers connected to the multiplexer isselectively output to the AD converter, the AD converter is caused toperform only the AD conversion process for the analog voltage signaloutput from the multiplexer, the number of pulses per unit time in aclock signal defining an operation timing of the AD converter is furtherreduced compared to that in the image reading operation, and in theirradiation start detection operation, in a case where power supplied tothe charge amplifier during the image reading operation is normal power,at least one of the part of charge amplifiers is further driven in a lowpower state in which power lower than the normal poser and greater than0 is supplied.

According to the invention, in the irradiation start detection operationof detecting irradiation start of radiation, the control unitselectively outputs the analog voltage signal from a part of the chargeamplifiers including a detection charge amplifier that is the chargeamplifier connected to the detection channel among the plurality ofcharge amplifiers connected to the multiplexer, to the AD converter, thecontrol unit causes the AD converter to perform only the AD conversionprocess for the analog voltage signal selectively output from themultiplexer, the control unit further reduces the number of pulses perunit time in a clock signal defining an operation timing of the ADconverter compared to that in the image reading operation, and, in theirradiation start detection operation, in a case where power supplied tothe charge amplifier during the image reading operation is normal power,the control unit further drives at least one of the part of chargeamplifiers in a low power state in which power lower than the normalpower and greater than 0 is supplied. Accordingly, it is possible toprovide a radiographic image detection device that can reduce the powerconsumption of the signal processing circuit in the irradiation startdetection operation and a method for operating the same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an X-ray imaging system.

FIG. 2 is a diagram illustrating an imaging order.

FIG. 3 is a diagram illustrating a menu and condition table.

FIG. 4 is an external perspective view illustrating an electroniccassette.

FIG. 5 is a block diagram illustrating an electrical configuration ofthe electronic cassette.

FIG. 6 is a circuit diagram illustrating a CA and a CDS.

FIG. 7 is a block diagram illustrating a gate driving unit, a MUX unit,and an ADC unit in detail.

FIG. 8 is a diagram illustrating a chip on which four adjacent ADCs thatare in charge of adjacent areas are mounted.

FIG. 9 is a diagram illustrating the procedure of the reading of adigital signal by a first MUX and a first ADC. (A) of FIG. 9 illustratesan aspect in which a digital signal corresponding to a first column isread, (B) of FIG. 9 illustrates an aspect in which a digital signalcorresponding to a second column is read, (C) of FIG. 9 illustrates anaspect in which a digital signal corresponding to a third column isread, and (D) of FIG. 9 illustrates an aspect in which a digital signalcorresponding to a 144th column is read.

FIG. 10 is a diagram illustrating the flow of an operation performed bya control unit.

FIG. 11 is a diagram illustrating gate pulses in a pixel reset operationand an image reading operation.

FIG. 12 is a diagram illustrating a power supply state of the ADC in theimage reading operation.

FIG. 13 is a diagram illustrating gate pulses in an AED operation.

FIG. 14 is a diagram illustrating the power supply state of the ADC inthe AED operation.

FIG. 15 is a graph illustrating the supply of power to the ADC.

FIG. 16 is a graph illustrating the number of ADCs in a first state perunit time in the AED operation and the image reading operation.

FIG. 17 is a flowchart illustrating the procedure of the operation ofthe electronic cassette.

FIG. 18 is a diagram illustrating the power supply state of the ADC inthe AED operation in a (1-2)-th embodiment.

FIG. 19 is a diagram illustrating the power supply state of the ADC inthe AED operation in a (1-3)-th embodiment.

FIG. 20 is a diagram illustrating the power supply state of the ADC inthe AED operation in a (1-4)-th embodiment.

FIG. 21 is a diagram illustrating the power supply state of the ADC inthe AED operation in a (1-5)-th embodiment.

FIG. 22 is a diagram illustrating the power supply state of the ADC inthe AED operation in a (1-6)-th embodiment.

FIG. 23 is a diagram illustrating another example of the power supplystate of the ADC in the AED operation in the (1-6)-th embodiment.

FIG. 24 is a diagram illustrating the power supply state of the ADC inthe AED operation in a (1-7)-th embodiment.

FIG. 25 is a block diagram illustrating a (1-8)-th embodiment in which adetection channel that is a signal line connected to a detection pixelused for the AED operation is set.

FIG. 26 is a diagram illustrating the power supply state of the ADC inthe AED operation in the (1-8)-th embodiment.

FIG. 27 is a diagram illustrating another example of the power supplystate of the ADC in the AED operation in the (1-8)-th embodiment.

FIG. 28 is a diagram illustrating an example of the arrangement of thedetection pixels.

FIG. 29 is a block diagram illustrating an example of the detectionpixel used for only the AED operation.

FIG. 30 is a block diagram illustrating another example of the detectionpixel used for only the AED operation.

FIG. 31 is a block diagram illustrating still another example of thedetection pixel used for only the AED operation.

FIG. 32 is a diagram illustrating an example of the setting of thedetection pixel.

FIG. 33A is a flowchart illustrating the procedure of driving the CDS inthe image reading operation.

FIG. 33B is a flowchart illustrating the procedure of driving the CDS inthe AED operation.

FIG. 34 is a circuit diagram illustrating another example of theconnection of the CDS, the MUX, and the ADC.

FIG. 35 is a graph illustrating a temperature distribution in a columndirection of a signal processing circuit.

FIG. 36 is a graph illustrating a charge component of a detectionchannel.

FIG. 37 is a diagram illustrating a (1-12)-th embodiment in which leakcharge correction and temperature drift correction are performed.

FIG. 38A is a diagram illustrating an AED operation according to a(1-13)-th embodiment in which a digital signal transmission I/F isswitched.

FIG. 38B is a diagram illustrating an image reading operation accordingto the (1-13)-th embodiment.

FIG. 39A is a diagram schematically illustrating the configuration of a(2-1)-th embodiment.

FIG. 39B is a graph illustrating the supply of power to the CA.

FIG. 40 is a flowchart illustrating the procedure of the operation of anelectronic cassette according to the (2-1)-th embodiment.

FIG. 41 is a graph illustrating another example of the supply of powerto the CA.

FIG. 42A is a diagram illustrating the configuration of a non-detectionchannel in a case in which a non-detection CA is changed to a power-offstate in the AED operation.

FIG. 42B is a diagram illustrating the configuration of thenon-detection channel in a case in which the non-detection CA is changedto the power-off state in the image reading operation.

FIG. 43 is a graph illustrating still another example of the supply ofpower to the CA.

FIG. 44 is a diagram illustrating the procedure of the reading of a dosesignal by the first MUX and the first ADC in a (3-1)-th embodiment. (A)of FIG. 44 illustrates an aspect in which a dose signal corresponding toa first column is read, (B) FIG. 44 illustrates an aspect in which adose signal corresponding to a third column is read, (C) of FIG. 44illustrates an aspect in which a dose signal corresponding to a fifthcolumn is read, and (D) of FIG. 44 illustrates an aspect in which a dosesignal corresponding to a 143rd column is read.

FIG. 45 is a graph illustrating the number of pulses per unit time inthe clock signal of the ADC.

FIG. 46 is a diagram illustrating a first method that reduces the numberof pulses per unit time in the clock signal of the ADC in the AEDoperation to be less than that in the image reading operation. (A) ofFIG. 46 illustrates the clock signal in the image reading operation and(B) of FIG. 46 illustrates the clock signal in the AED operation.

FIG. 47 is a diagram illustrating a second method that reduces thenumber of pulses per unit time in the clock signal of the ADC in the AEDoperation to be less than that in the image reading operation. (A) ofFIG. 47 illustrates the clock signal in the image reading operation and(B) of FIG. 47 illustrates the clock signal in the AED operation.

FIG. 48 is a flowchart illustrating the procedure of the operation of anelectronic cassette according to the (3-1)-th embodiment.

FIG. 49A is a diagram illustrating a circuit configuration of adetection channel in the AED operation in a (3-2)-th embodiment.

FIG. 49B is a diagram illustrating a circuit configuration of adetection channel in the image reading operation in the (3-2)-thembodiment.

FIG. 50A is a diagram illustrating the power supply state of a block ina case in which the reading of charge starts immediately after the blockis switched from a non-operating state to an operating state.

FIG. 50B is a diagram illustrating the power supply state of a block ina case in which the block is switched from the non-operating state tothe operating state a predetermined time before the timing when thereading of charge starts.

FIG. 51 is a flowchart illustrating the procedure of the operation of anelectronic cassette according to a (4-1)-th embodiment.

FIG. 52 is a diagram illustrating in detail the period for which chargeis read in a case in which the signal lines in all of the areas that theblocks are in charge of are the detection channels.

FIG. 53 is a diagram illustrating in detail the period for which chargeis read in a case in the odd-numbered columns are the detection channelsand the MUX is a general MUX having only a function of sequentiallyselecting the detection channels one by one.

FIG. 54 is a diagram illustrating in detail the period for which chargeis read in a case in the odd-numbered columns are the detection channelsand the MUX has a function of selecting only the analog voltage signalfrom the detection CA of the detection channel.

FIG. 55 is a diagram illustrating an example in which each block isswitched from the operating state to the non-operating state before thereading of charge in each block starts.

FIG. 56 is a diagram illustrating an example in which each block isswitched from the operating state to the non-operating state after thereading of charge in each block ends.

FIG. 57 is a diagram illustrating an example in which each block isswitched from the operating state to the non-operating state between theintermittent periods for which charge is read in each block.

FIG. 58 is a diagram illustrating a (4-3)-th embodiment in which all ofthe blocks are changed to the operating state until the image readingoperation starts after the start of the emission of X-rays is detectedin the AED operation.

FIG. 59 is a graph illustrating the supply of power to the CA.

FIG. 60 is a flowchart illustrating the procedure of the operation of anelectronic cassette according to a fifth invention.

FIG. 61 is a graph illustrating the number of pulses per unit time inthe clock signal of the ADC.

FIG. 62 is a flowchart illustrating the procedure of the operation of anelectronic cassette according to a sixth invention.

FIG. 63 is a diagram illustrating the circuit configuration of a blockand the periphery thereof and a state in the image reading operation ina seventh invention.

FIG. 64 is a diagram illustrating the circuit configuration of the blockand the periphery thereof and a state in the AED operation in theseventh invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. First Invention (1-1)-thEmbodiment

In FIG. 1, an X-ray imaging system 10 that performs imaging using X-raysas radiation comprises an X-ray generation apparatus 11 and an X-rayimaging apparatus 12 and is installed in, for example, an imaging roomof a radiology department in a medical facility. The X-ray generationapparatus 11 includes an X-ray source 13, a radiation source controldevice 14 that controls the X-ray source 13, and an irradiation switch15 that is connected to the radiation source control device 14. TheX-ray imaging apparatus 12 includes an electronic cassette 16 which is aradiographic image detection device and a console 17.

In addition to the X-ray imaging system 10, an upright imaging table 18for capturing an image of a patient P that is a subject at an uprightposture and a decubitus imaging table 19 for capturing an image of thepatient P at a decubitus posture are installed in the imaging room. TheX-ray source 13 is shared by the upright imaging table 18 and thedecubitus imaging table 19. In addition, FIG. 1 illustrates an aspect inwhich the electronic cassette 16 is set in the upright imaging table 18and an X-ray image of the patient P is captured at the upright posture.

As is well known, the X-ray source 13 includes an X-ray tube thatgenerates X-rays and an irradiation field limiter (also referred to as acollimator) that limits the irradiation field of the X-rays generated bythe X-ray tube to the patient P. The radiation source control device 14controls the tube voltage, tube current, and X-ray emission time of theX-ray tube. The radiation source control device 14 stores in advance aplurality of types of X-ray emission conditions including the tubevoltage, the tube current, and the irradiation time according to animaging part, such as the chest or the abdomen, such that an operatorselects a desired irradiation condition from the stored irradiationconditions and inputs the selected irradiation condition. The operatorcan finely adjust the irradiation conditions considering, for example,the body shape of the patient P.

The irradiation switch 15 is operated by the operator in a case in whichthe emission of X-rays starts. The irradiation switch 15 is a two-stagepressure type. In a case in which the irradiation switch 15 is pressedto the first stage (pressed halfway), the radiation source controldevice 14 instructs the X-ray source 13 to start a preparation operationbefore X-rays are emitted. In a case in which the irradiation switch 15is pressed to the second stage (pressed fully), the radiation sourcecontrol device 14 instructs the X-ray source 13 to start the emission ofX-rays. The radiation source control device 14 includes a timer thatstarts to measure time in a case in which the emission of X-rays isstarted and stops the emission of X-rays by the X-ray source 13 in acase in which the time measured by the timer reaches the irradiationtime set in the irradiation conditions.

The electronic cassette 16 detects an X-ray image based on the X-raysthat have been emitted from the X-ray source 13 and then transmittedthrough the patient P. For example, the console 17 is configured byinstalling a control program, such as an operating system, or variousapplication programs in a computer, such as a notebook personalcomputer. The console 17 includes a display 20 and an input device 21such as a touch pad or a keyboard. The console 17 displays variousoperation screens provided with an operation function based on agraphical user interface (GUI) on the display 20 and receives variousoperation commands input from the input device 21 by the operatorthrough the various operation screens.

The electronic cassette 16 and the console 17 comprise wirelesscommunication units 22 and 23 for performing wireless communicationtherebetween, respectively. The electronic cassette 16 and the console17 transmit and receive various kinds of information including animaging menu or X-ray images through the wireless communication units 22and 23, using wireless communication.

Each of the wireless communication units 22 and 23 includes, forexample, an antenna, a modulation and demodulation circuit, and atransmission control unit. The modulation and demodulation circuitperforms modulation for imposing data to be transmitted onto a carrierwave (also referred to as a carrier) and demodulation for extractingdata from the carrier wave received by the antenna. The transmissioncontrol unit performs transmission control based on a wireless localarea network (LAN).

The console 17 receives the input of an imaging order to command theoperator to perform X-ray imaging. For example, the imaging order isinput from a radiology information system (RIS) (not illustrated) to theconsole 17.

In FIG. 2, the imaging order has items, such as an order ID(identification data), a patient ID, and an imagingpart/posture/direction. The order ID is a symbol or a number foridentifying each imaging order and is automatically assigned by the RIS.A patient ID of the patient P that is an imaging target is written inthe patient ID item. The patient ID is a symbol or a number foridentifying each patient P.

The imaging part, posture, and imaging direction designated by thedoctor who has issued the imaging order are written in the imagingpart/posture/direction item. The imaging part is a part of the humanbody, such as the head, the cervical vertebra, the chest, the abdomen, ahand, a finger, the elbow, or the knee. The posture is the posture ofthe patient P, such as an upright posture, a decubitus posture, or asitting posture and the imaging direction is the direction of thepatient P with respect to X-rays, such as the front, the side, and theback. The imaging order includes patient information items (notillustrated), such as the name, sex, age, height, and weight of thepatient P, in addition to the above-mentioned items. In addition, itemsincluding a diagnosis and treatment department that has issued theimaging order, the doctor who has issued the imaging order, the date andtime when the imaging order was received by the RIS, the purpose ofimaging, such as postoperative follow-up or therapeutic effectevaluation, and items to be handed over from the doctor to the operatormay be provided.

One imaging order may be issued for one patient P or a plurality ofimaging orders may be issued for one patient P at the same time. In acase in which a plurality of imaging orders are issued for one patient Pat the same time, an identification code indicating that the imagingorders are for one patient P is attached to the order IDs of theplurality of imaging orders.

The console 17 stores a menu and condition table 25 illustrated in FIG.3. An imaging menu having a set of the imaging part, the posture, andthe imaging direction and irradiation conditions corresponding to theimaging menu are registered in the menu and condition table 25 so as tobe association with each other. In addition, an imaging menu having aset of the imaging part and the imaging direction obtained by excludingthe posture from the above-mentioned imaging menu or an imaging menucorresponding to special imaging, such as tomosynthesis imaging, may beprovided.

The console 17 displays an imaging order list which is a list of thecontent of the imaging order illustrated in FIG. 2 on the display inresponse to the operation of the operator. The operator browses theimaging order list and checks the content of the imaging order. Then,the console 17 displays the content of the menu and condition table 25on the display in a form in which the imaging menu can be set. Theoperator selects an imaging menu matched with the imagingpart/posture/direction designated by the imaging order and sets theimaging menu. In addition, the operator sets the irradiation conditionsmatched with the irradiation conditions corresponding to the selectedimaging menu in the radiation source control device 14.

The console 17 transmits various kinds of information, such as theimaging menu set by the operator, the irradiation conditionscorresponding to the set imaging menu, the order ID, and a console IDwhich is a symbol or a number for identifying the console, as imagingpreparation commands to the electronic cassette 16 through the wirelesscommunication unit 23.

In addition, the console 17 converts the X-ray image from the electroniccassette 16 into an image file with a format based on, for example, theDigital Imaging and Communication in Medicine (DICOM) standard andtransmits the image file to a picture archiving and communication system(PACS) (not illustrated). In the image file, the X-ray image and imageaccessory information including, for example, an order ID, patientinformation, an imaging menu, irradiation conditions, and a cassette IDwhich is a symbol or a number for identifying the electronic cassette 16are associated with one image ID. The doctor in the diagnosis andtreatment department that has issued the imaging order can access thePACS with a terminal in the diagnosis and treatment department, downloadthe image file, and browse the X-ray image.

In FIG. 4, the electronic cassette 16 includes a sensor panel 30, acircuit unit 31, and a portable housing 32 that has a rectangularparallelepiped shape and accommodates the sensor panel 30 and thecircuit unit 31. The housing 32 has a size that is based on theInternational Organization for Standardization (ISO) 4090:2001 and isalmost the same as that of, for example, a film cassette, an imagingplate (IP) cassette, or a computed radiography (CR) cassette. Thehousing 32 accommodates, for example, a battery 65 (see FIG. 5) thatsupplies power to the wireless communication unit 22 and each unit ofthe electronic cassette 16 and a wired communication unit 66 (see FIG.5) that is connected to the console 17 through a cable in a wiredmanner, in addition to the sensor panel 30 and the circuit unit 31. In acase in which the wireless communication unit 22 is used, the electroniccassette 16 is driven by power from the battery 65 and can be used in aso-called wireless manner.

A rectangular opening is formed in a front surface 32A of the housing 32and a transmission plate 33 that transmits X-rays is attached to theopening. The electronic cassette 16 is positioned at a posture where thefront surface 32A faces the X-ray source 13. The housing 32 is providedwith a switch for switching between turn-on and the turn-off the powersupply or an indicator for indicating an operation state of theelectronic cassette 16 such as the remaining usage time of the battery65 or an imaging preparation completion state.

The sensor panel 30 includes a scintillator 34 and a light detectionsubstrate 35. The scintillator 34 and the light detection substrate 35are stacked in the order of the scintillator 34 and the light detectionsubstrate 35 as viewed from the front surface 32A on which X-rays areincident. The scintillator 34 includes a phosphor, such as thalliumactivated cesium iodide (CsI:Tl) or terbium activated gadoliniumoxysulfide (Gd₂O₂S:Tb (GOS)), converts X-rays incident through thetransmission plate 33 into visible light, and emits the visible light.In addition, a sensor panel in which the light detection substrate 35and the scintillator 34 are stacked in this order as viewed from thefront surface 32A on which X-rays are incident may be used. Further, adirect-conversion-type sensor panel may be used which directly convertsX-rays into charge using a photoconductive film such as amorphousselenium.

The light detection substrate 35 detects the visible light emitted fromthe scintillator 34 and converts the visible light into charge. Thecircuit unit 31 controls the driving of the light detection substrate 35and generates an X-ray image on the basis of the charge output from thelight detection substrate 35.

In FIG. 5, the light detection substrate 35 is configured by providingpixels 40 which are arranged in a two-dimensional matrix of N rows and Mcolumns, N gate lines 41, and M signal lines 42 on a glass substrate(not illustrated). The gate lines 41 extend in the X direction along therow direction of the pixels 40 and are arranged at predetermined pitchesin the Y direction along the column direction of the pixels 40. Thesignal lines 42 extend in the Y direction and are arranged atpredetermined pitches in the X direction. The gate lines 41 and thesignal lines 42 are orthogonal to each other and the pixels 40 areprovided at the intersection points between the gate lines 41 and thesignal lines 42.

Here, N and M are integers equal to or greater than 2. In this example,a case in which N is 2880 and M is 2304 (see FIG. 7) will be described.The numbers of rows and columns of the pixels 40 are not limitedthereto. The array of the pixels 40 may not be a square array asillustrated in FIG. 5. Alternatively, the pixels 40 may be inclined atan angle of 45° and may be arranged in zigzag.

As is well known, each pixel 40 comprises a photoelectric conversionunit 43 on which visible light is incident and which generates charge(electronic-hole pair) and accumulates the charge and a thin filmtransistor (TFT) 44 which is a switching element. The photoelectricconversion unit 43 has a structure in which an upper electrode and alower electrode are provided on the upper and lower sides of asemiconductor layer that generates charge. The semiconductor layer is,for example, a p-intrinsic-n (PIN) type. An N-type layer is formed onthe upper electrode side and a P-type layer is formed on the lowerelectrode side. The TFT 44 has a gate electrode connected to the gateline 41, a source electrode connected to the signal line 42, and a drainelectrode connected to the lower electrode of the photoelectricconversion unit 43. Instead of the TFT type, a complementary metal oxidesemiconductor (CMOS) sensor panel may be used as the switching element.

A bias line (not illustrated) is connected to the upper electrode of thephotoelectric conversion unit 43. A positive bias voltage is applied tothe upper electrode through the bias line. The electric field isgenerated in the semiconductor layer by the application of the positivebias voltage. Therefore, among the electronic-hole pairs generated inthe semiconductor layer by photoelectric conversion, the electron ismoved to the upper electrode and is then absorbed to the bias line andthe hole is moved to the lower electrode and is collected as charge.

The circuit unit 31 is provided with a gate driving unit 50, a signalprocessing circuit 51, a memory 52, a power supply unit 53, and acontrol unit 54 that controls these units.

The gate driving unit 50 is connected to the end of each gate line 41and generates a gate pulse G(R) (R=1 to N) for driving the TFT 44. Thecontrol unit 54 drives the TFT 44 through the gate driving unit 50 andcontrols the signal processing circuit 51 so as to perform a pixel resetoperation which reads dark charge from the pixel 40 and resets (discard)the dark charge, a pixel charge accumulation operation which accumulatescharge corresponding to the amount of incident X-rays in the pixel 40,an image reading operation which reads an X-ray image for diagnosis, andan AED operation which detects the start of the emission of X-rays.

The image reading operation is an operation which reads charge from thepixel 40 through the signal line 42 after a pixel charge accumulationperiod elapses from the start of the emission of X-rays and outputs anX-ray image represented by a digital signal corresponding to the readcharge. The AED operation is an operation which reads the charge fromthe pixel 40 through the signal line 42 from before start of theemission of X-rays and detects the start of the emission of X-rays onthe basis of a digital signal corresponding to the read charge.

The signal processing circuit 51 reads an analog voltage signal V(C)(C=1 to M) corresponding to the charge from the pixel 40 through thesignal line 42 to perform signal processing. The signal processingcircuit 51 includes a CA 60, a correlated double sampling circuit(hereinafter, referred to as a CDS) 61, a MUX unit 62, and an ADC unit63.

The CA 60 is provided for each signal line 42 and is connected to oneend of the signal line 42. The CA 60 outputs the analog voltage signalV(C) corresponding to the charge input from the pixel 40 through thesignal line 42. The CDS 61 is provided for each signal line 42,similarly to the CA 60. The CDS 61 performs a known correlated doublesampling process for the analog voltage signal V(C) from the CA 60 toremove a reset noise component of the CA 60 from the analog voltagesignal V(C).

The CA 60 is connected to the MUX unit 62. The CDS 61 is providedbetween the CA 60 and the MUX unit 62. In addition, the ADC unit 63 isconnected to a stage behind the MUX unit 62. The MUX unit 62sequentially selects the analog voltage signals V(C) input from aplurality of CAs 60 through the CDSs 61 and outputs the selected analogvoltage signal V(C) to the ADC unit 63. The ADC unit 63 performs an ADconversion process that converts the analog voltage signal V(C) from theMUX unit 62 into a digital signal DS(C) corresponding to the voltagevalue of the analog voltage signal V(C). Then, the ADC unit 63 outputsthe converted digital signal DS(C) to the memory 52. The memory 52stores the digital signal DS(C) from the ADC unit 63. The memory 52 hasa capacity to store an X-ray image corresponding to at least one screen.

The power supply unit 53 supplies power from the battery 65 to each unitunder the control of the control unit 54. For example, the battery 65 isattachably and detachably provided on the rear surface opposite to thefront surface 32A of the housing 32.

The control unit 54 receives various kinds of information from theconsole 17 through the wireless communication unit 22 or the wiredcommunication unit 66 and performs control corresponding to the variouskinds of information. For example, the control unit 54 changes theprocessing conditions of the signal processing circuit 51 according tothe irradiation conditions.

In FIG. 6, the CA 60 includes an operational amplifier 70, a capacitor71, and an amplifier reset switch 72. The operational amplifier 70 hastwo input terminals and one output terminal. The signal line 42 isconnected to one of the two input terminals and a ground line isconnected to the other input terminal. The capacitor 71 and theamplifier reset switch 72 are connected in parallel between the inputterminal to which the signal line 42 is connected and the outputterminal.

The CA 60 accumulates the charge input from the signal line 42 in thecapacitor 71 to integrate the charge and outputs a voltage valuecorresponding to the integrated value, that is, the analog voltagesignal V(C). The driving of the amplifier reset switch 72 is controlledby the control unit 54. The amplifier reset switch 72 is turned on toreset (discard) the charge accumulated in the capacitor 71.

The CDS 61 includes a first sample-and-hold circuit (hereinafter,abbreviated to S/H) 73A, a second S/H 73B, and a difference amplifier74. The first S/H 73A samples and holds the reset noise component of theCA 60 in a case in which the TFT 44 is in an off state. The second S/H73B samples and holds the analog voltage signal V(C) output from the CA60 on the basis of the charge input in a case in which the TFT 44 is inan on state. The difference amplifier 74 calculates the differencebetween the reset noise components held in the S/Hs 73A and 73B and theanalog voltage signal V(C). Therefore, the analog voltage signal V(C)from which noise has been removed is output.

In FIG. 7, the gate driving unit 50 includes, for example, a total of 12gate driving circuits 75, that is, the first to twelfth gate drivingcircuits 75. Each gate driving circuit 75 corresponds to each gate line41. Since N which is the number of rows of pixels 40 is 2880, 240(=2880/12) gate lines 41 are connected to one gate driving circuit 75.For example, the gate lines 41 corresponding to the first to 240th rowsof the pixels 40 are connected to the first gate driving circuit 75 andthe gate lines 41 corresponding to the 241st to 480th rows of the pixels40 are connected to the second gate driving circuit 75. One gate drivingcircuit 75 is in charge of reading charge from 240 rows of the pixels40.

The MUX unit 62 includes, for example, a total of 16 MUXs 76, that is,the first to sixteenth MUXs 76. Each MUX 76 corresponds to each signalline 42. Since M which is the number of columns of the pixels 40 is2304, 144 (=2304/16) signal lines 42 are connected to one MUX 76. Forexample, the signal lines 42 corresponding to the first to 144th columnsof the pixels 40 are connected to the first MUX 76 and the signal lines42 corresponding to the 145th to 288th columns of the pixels 40 areconnected to the second MUX 76. Therefore, one MUX 76 selectivelyoutputs the analog voltage signals V(C) based on the charge from 144columns of the pixels 40. Hereinafter, an area formed by the pixels 40connected to a plurality of adjacent signal lines 42 is referred to asan area AR (AR1 to AR16).

Each MUX 76 includes a plurality of input terminals. A plurality of CAs60 are connected to the plurality of input terminals with the CDSs 61interposed therebetween.

The ADC unit 63 includes a total of 16 ADCs 77, that is, the first tosixteenth ADCs 77, similarly to the first to sixteenth MUXs 76 of theMUX unit 62. The first to sixteenth ADCs 77 are connected to a stagebehind the first to sixteenth MUXs 76. Since the first to sixteenth MUXs76 are provided so as to correspond to the areas AR1 to AR16,respectively, the first to sixteenth ADCs 77 are also provided so as tocorrespond to the areas AR1 to AR16, respectively.

One ADC 77 is in charge of an AD conversion process into the digitalsignals DS(V) based on the charge from 144 columns of the pixels 40. Forexample, the first ADC 77 converts the analog voltage signals V(1) toV(144) sequentially output from the first MUX 76 into the digitalsignals DS(1) to DS(144) and the second ADC 77 converts the analogvoltage signals V(145) to V(288) sequentially output from the second MUX76 into the digital signal DS(145) to DS(288).

As illustrated in FIG. 8, one MUX 76, a plurality of CAs 60 and CDSs 61connected to the input terminals of the MUX 76, and one ADC 77 connectedto the output terminal of the MUX 76 form one block BL. There are 16blocks BL whose number is the same as the number of areas AR.

As represented by a dashed line, blocks BL1 to BL4 formed by the CAs 60,the CDSs 61, the MUXs (first to fourth MUXs) 76, and the ADCs (first tofourth ADCs) 77 that take charge of each of four adjacent areas AR1 toAR4 are mounted on the same chip CP1. Similarly, blocks BL5 to BL8formed by the CAs 60, the CDSs 61, the MUXs (fifth to eighth MUXs) 76,and the ADCs (fifth to eighth ADCs) 77 that take charge of each of areasAR5 to AR8 are mounted on a chip CP2. Blocks BL9 to BL12 formed by theCAs 60, the CDSs 61, the MUXs (ninth to twelfth MUXs) 76, and the ADCs(ninth to twelfth ADCs) 77 that take charge of each of areas AR9 to AR12are mounted on a chip CP3. Blocks BL13 to BL16 formed by the CAs 60, theCDSs 61, the MUXs (thirteenth to sixteenth MUXs) 76, and the ADCs(thirteenth to sixteenth ADCs) 77 that take charge of each of areas AR13to AR16 are mounted on a chip CP4. These chips CP1 to CP4 are physicallycompletely separated from each other.

The number of gate driving circuits 75 and the number of rows of thepixels 40 that one gate driving circuit 75 is in charge of are notlimited to 12 and 240 in this example, respectively. Similarly, thenumber of MUXs 76 and ADCs 77 (the number of blocks BL), the number ofcolumns of the pixels 40 that one MUX 76 and one ADC 77 are in charge of(the number of columns of the pixels 40 included in one block BL), andthe number of blocks BL forming one chip CP are not limited to thisexample and may be any values. For example, the number of columns of thepixels 40 included in one block BL may be 256 and the number of blocksBL may be 9. In addition, the number of columns of the pixels 40included in one block BL may be 128 and the number of blocks BL may be18.

FIG. 9 illustrates, for example, a procedure of reading the digitalsignals DS(1) to DS(144) in the area AR1 corresponding to the first to144th columns. FIG. 9 illustrates a state in which the analog voltagesignals V(1) to V(144), from which reset noise has been removed andwhich correspond to the charge read from the pixels 40 through thesignal lines 42, appear in the output terminals of the CDSs 61.

In this state, first, as illustrated in (A) of FIG. 9, the first MUX 76selects the analog voltage signal V(1) corresponding to the firstcolumn. Then, the analog voltage signal V(1) is input to the first ADC77 and the first ADC 77 converts the analog voltage signal V(1) into thedigital signal DS(1). Then, as illustrated in (B) of FIG. 9, the firstMUX 76 selects the analog voltage signal V(2) corresponding to thesecond column. Then, the analog voltage signal V(2) is input to thefirst ADC 77 and the first ADC 77 converts the analog voltage signalV(2) into the digital signal DS(2). Then, as illustrated in (C) of FIG.9, the first MUX 76 selects the analog voltage signal V(3) correspondingto the third column. Then, the analog voltage signal V(3) is input tothe first ADC 77 and the first ADC 77 converts the analog voltage signalV(3) into the digital signal DS(3).

This series of operations is repeatedly performed in the first MUX 76and the first ADC 77. Finally, as illustrated in (D) of FIG. 9, theanalog voltage signal V(144) corresponding to the 144th column isconverted into the digital signal DS(144) and the reading of the digitalsignals DS(1) to DS(144) in the area AR1 corresponding to the first to144th columns ends. This holds for each MUX 76 and each ADC 77 in theother areas AR2 to AR16.

As illustrated in FIG. 10, the control unit 54 starts the AED operationin a case in which it receives an imaging preparation command in variouskinds of information including the imaging menu from the console 17 fromthe wireless communication unit 22 or the wired communication unit 66.In the AED operation, the charge generated by the photoelectricconversion unit 43 of the pixel 40 is converted into the digital signalDS(C) by the signal processing circuit 51 and is then stored in thememory 52. Hereinafter, the digital signal DS(C) stored in the memory 52by the AED operation is referred to as a dose signal DDS(C). The controlunit 54 performs a standby operation before it receives the imagingpreparation command. The standby operation is a state in which only abias voltage is applied to the upper electrode of the photoelectricconversion unit 43 and no power is supplied to, for example, the signalprocessing circuit 51.

The dose signal DDS(C) is repeatedly read at predetermined intervals.The dose signal DDS(C) obtained by one reading operation corresponds tothe incident dose of X-rays per unit time. In a case in which theemission of X-rays starts, the incident dose of X-rays per unit timeincreases gradually. Therefore, the value of the dose signal DDS (C)also increases with the increase in the incident dose.

Whenever the dose signal DDS(C) is stored in the memory 52, the controlunit 54 reads the dose signal DDS(C) from the memory 52 and compares thedose signal DDS(C) with a predetermined irradiation start determinationthreshold value. In a case in which the dose signal DDS(C) is greaterthan the irradiation start determination threshold value, the controlunit 54 determines that the emission of X-rays has started. Therefore,the electronic cassette 16 can detect the start of the emission ofX-rays, without receiving the timing signal for indicating the emissionstart timing of X-rays from the radiation source control device 14.

In a case in which the start of the emission of X-rays has beendetected, the control unit 54 performs a pixel reset operation (notillustrated in FIG. 10) and then performs a pixel charge accumulationoperation. The control unit 54 includes a timer that starts themeasurement of time in a case in which the start of the emission ofX-rays has been detected, similarly to the radiation source controldevice 14, and determines that the emission of X-rays has ended in acase in which the time measured by the timer has reached the irradiationtime of the irradiation conditions set in the console 17. In a case inwhich the control unit 54 detects the end of the emission of X-rays, itends the pixel charge accumulation operation and performs an imagereading operation. In this way, one X-ray imaging operation forobtaining an X-ray image corresponding to one screen ends. After theimage reading operation ends, the control unit 54 returns to the standbyoperation again.

As illustrated in FIG. 11, in the pixel reset operation and the imagereading operation, the gate driving circuit 75 sequentially applies thegate pulse G(R) to each of the first to 2880th gate lines 41. In thepixel reset operation, charge flows from the pixel 40 to the capacitor71 of the CA 60 through the signal line 42 and is accumulated in thecapacitor 71. The charge is discarded by the amplifier reset switch 72without being read.

In contrast, in the image reading operation, as illustrated in FIG. 9,the digital signal DS(C) based on the charge from the pixel 40 is readand stored as an X-ray image provided for diagnosis in the memory 52.Hereinafter, the digital signal DS(C) read by the image readingoperation is represented by an image signal DIS(C) so as to bedistinguished from the dose signal DDS(C) in the AED operation.

As illustrated in FIG. 12, the control unit 54 changes all of the firstto sixteenth ADCs 77 to an operating state (corresponding to a firststate) during the image reading operation. Then, the control unit 54operates the first to sixteenth ADCs 77 in parallel at the same timingduring the image reading operation. The control unit 54 also changes thefirst to sixteenth MUXs 76 connected to the first to sixteenth ADCs 77to the operating state during the image reading operation and operatesthe first to sixteenth MUXs 76 in parallel at the same time. Therefore,in the image reading operation, the image signals DIS(C) correspondingto the same columns are sequentially read at the same timing from thefirst column to the last column in each of the areas AR1 to AR16. Forexample, the image signals DIS(1), DIS(145), DIS(289), . . . , DIS(2161)corresponding to the first column, the 145th column, the 289th column, .. . , the 2161st column which are the first columns in the areas AR1 toAR16 are read at the same timing. In addition, all of the CAs 60 and theCDSs 61 connected to the first to sixteenth MUXs 76 are also changed tothe operating state during the image reading operation.

In the standby operation after the image reading operation ends, thecontrol unit 54 changes all of the first to sixteenth ADCs 77 to anon-operating state (corresponding to a second state). All of the firstto sixteenth MUXs 76, the CAs 60, and the CDSs 61 are changed to thenon-operating state during the standby operation.

As illustrated in FIG. 13, in the AED operation, the gate pulses G(R)are sequentially applied to the gate lines 41 corresponding to the samerows at the same time from the first row to the last row that each ofthe first to twelfth gate driving circuits 75 is in charge of. Forexample, the gate pulses G(1), G(241), G(481), . . . , G(2639) areapplied to the gate lines 41 corresponding to the first row which is thefirst row of the first gate driving circuit 75, the 241st row which isthe first row of the second gate driving circuit 75, the 481st row whichis the first row of the third gate driving circuit 75, . . . , the2639th row which is the first row of the twelfth gate driving circuit 75at the same time. Then, the gate pulses G(2), G(242), G(482), . . . ,G(2640) are applied to the gate lines 41 corresponding to the second,242nd, 482nd, . . . , 2640th rows which are the rows following the firstrow at the same time.

As such, in the AED operation, the gate pulse G(R) is applied to thegate lines 41 corresponding to a total of 12 rows which are arranged atan interval of 240 rows. Therefore, the TFTs 44 in 12 rows aresimultaneously turned on and charge from the pixels 40 in 12 rows isadded in the signal line 42 corresponding to each column and is theninput to the CA 60. Therefore, in a case in which the same charge isgenerated in each pixel 40, the dose signal DDS(C) obtained by the AEDoperation is approximately 12 times the image signal DIS(C) obtained bythe image reading operation. As a result, it is possible to improve thesignal-to-noise (S/N) ratio of the dose signal DDS(C).

Whenever the dose signal DDS(C) based on the charge corresponding to 12rows is stored in the memory 52, the control unit 54 compares the dosesignal DDS(C) with the irradiation start determination threshold valueto determine whether the emission of X-rays has started. The dosesignals DDS(C) corresponding to 2304 columns are output. The controlunit 54 compares one representative value among 2304 dose signals withthe irradiation start determination threshold value. The representativevalue is, for example, an average value, a maximum value, or a modevalue of 2304 dose signals.

In the pixel charge accumulation operation, the gate driving circuit 75does not apply the gate pulse G(R) to the gate line 41 and all of theTFTs 44 of the pixels 40 are in an off state.

In the pixel reset operation, the gate pulse G(R) may not besequentially applied to each gate line 41 unlike FIG. 11 and the firstto twelfth gate driving circuits 75 may sequentially apply the gatepulses G(R) to the corresponding first to last rows such that the gatepulse G(R) is applied to the gate lines 41 corresponding to the samerows at the same time, as illustrated in FIG. 13. Alternatively, thegate pulses G(R) is applied to each gate line 41 at the same time tocollectively read charge from all of the pixels 40.

As illustrated in FIG. 14, the control unit 54 periodically switches thepower supply state of the first to sixteenth ADCs 77, specifically, theoperating state and the non-operating state during the AED operation. Inaddition, the control unit 54 shifts the switching timing of the powersupply state of the first to sixteenth ADCs 77. Specifically, first, thecontrol unit 54 changes the first, fifth, ninth, and thirteenth ADCs 77which are the first ADCs in the chips CP1 to CP4 to the operating stateand then switches the operating state to the non-operating state afterthe lapse of a time T. The control unit 54 changes the second, sixth,tenth, and fourteenth ADCs 77 adjacent to the above-mentioned ADCs tothe operating state at the same time as the switching and similarlyswitches the operating state to the non-operating state after the lapseof the time T. Then, the control unit 54 operates the third, seventh,eleventh, and fifteenth ADCs 77 for the time T and then operates thefourth, eighth, twelfth, and sixteenth ADCs 77 which are the last ADCsin the chips CP1 to CP4 for the time T. Then, the control unit 54repeats the series of power supply state switching operations.

Since the first to sixteenth ADCs 77 are provided for the areas AR1 toAR16, respectively, FIG. 14 illustrates a case in which the power supplystate of the ADC 77 is switched in units of the ADCs 77 that are incharge of the areas AR. The first, fifth, ninth, and thirteenth ADCs 77,the second, sixth, tenth, and fourteenth ADCs 77, the third, seventh,eleventh, and fifteenth ADCs 77, and the fourth, eighth, twelfth, andsixteenth ADCs 77 correspond to groups in which the power supply stateis switched at the same timing. In the groups, the timing of the powersupply state is shifted. In addition, three ADCs 77 are disposed betweentwo ADCs 77 belonging to the same group. For example, a total of threeADCs 77, that is, the second to fourth ADCs 77 are disposed between thefirst and fifth ADCs 77 forming the same group.

The time T is the time required to read the dose signals DDS(C) from allof 144 columns of the pixels 40 that each ADC 77 is in charge of in theAED operation. The time (hereinafter, referred to as a reading period ofthe dose signal DDS(C)) required to read the dose signal DDS(C) from allof 2304 columns is 4T (=T′4) since the dose signals DDS(C) are read fourtimes by the chips CP1 to CP4.

The dose signal DDS(C) obtained by the AED operation is not used as theimage information of the patient P unlike the image signal DIS(C)obtained by the image reading operation. Therefore, in the AEDoperation, as illustrated in FIG. 13, the gate pulse G(R) is applied tothe gate lines 41 corresponding to a total of 12 rows at the same timeand charge from the pixels 40 in 12 rows is added in the signal line 42corresponding to each column. As illustrated in FIG. 14, in the AEDoperation, the first to sixteenth ADCs 77 are not always in theoperating state unlike the image reading operation and the power supplystate is periodically switched.

Here, the operating state is a state in which power PON_A required tofulfill the function of the ADC 77 is supplied to the ADC 77 asillustrated on the right side in FIG. 15. The power PON_A corresponds tofirst power. That is, the operating state corresponds to the first stateas described above. In contrast, the non-operating state is a state inwhich power PSL_A which is lower than the power PON_A and at which theADC 77 is not capable of fulfilling its function is supplied to the ADC77 as illustrated on the right side in FIG. 15. The power PSL_Acorresponds to second power. That is, the non-operating statecorresponds to the second state as described above.

As illustrated in FIGS. 12 and 14, the control unit 54 has a function ofswitching the power supply state to the ADC 77 between the operatingstate which is the first state and the non-operating state which is thesecond state.

Specifically, the power PON_A required to fulfill the function of theADC 77 is power required for the image reading operation. In addition,the operating state may be a state in which power which is lower thanthe power required for the image reading operation and at which the ADC77 can fulfill the function is supplied.

In FIG. 15, the power PSL_A has a value equal to or greater than 0.However, the power PSL_A may be 0. That is, the non-operating state maybe a power-off state in which no power is supplied to the ADCs 77. Inaddition, the non-operating state may be a state in which the supply ofa clock signal defining the operation timing of the ADC 77 is stoppedsuch that the power consumption of the ADC 77 is substantially zero.

As illustrated in FIG. 12, in the image reading operation, all of thefirst to sixteenth ADCs 77 are always in the operating state. Therefore,in a case in the unit time is T, the number of ADCs 77 in the operatingstate (first state) per unit time T is 16. In contrast, as illustratedin FIG. 14, in the AED operation, since four of the first to sixteenthADCs 77 are operated at the same timing, the number of ADCs 77 in theoperating state per unit time T is 4. Therefore, as illustrated in FIG.16, in a case in which 16, which is the number of ADCs 77 per unit timeT in the image reading operation, is normalized to 1, the number of ADCs77 per unit time T in the AED operation is 0.25 (=4/16), which is lessthan that in the image reading operation.

The control unit 54 switches the power supply state of the CA 60, theCDS 61, and the MUX 76 that form the block BL together with the ADC 77in operative association with the ADC 77, which is not illustrated andwhose description will be omitted.

Next, the operation of the configuration will be described withreference to a flowchart illustrated in FIG. 17. In a case in which theoperator takes an X-ray image with the X-ray imaging system 10, theoperator turns on the electronic cassette 16. The control unit 54performs the standby operation (Step ST100).

The operator sets a desired imaging menu through the input device 21 ofthe console 17. Then, various kinds of information, such as the setimaging menu and the irradiation conditions corresponding to the setimaging menu, are transmitted as an imaging preparation command from theconsole 17 to the electronic cassette 16.

After setting the imaging menu, the operator sets the same irradiationconditions as the irradiation conditions corresponding to the setimaging menu or irradiation conditions obtained by finely adjusting theirradiation conditions corresponding to the set imaging menu accordingto, for example, the physique of the patient P in the radiation sourcecontrol device 14. The operator sets the electronic cassette 16 in oneof the upright imaging table 18 and the decubitus imaging table 19 andlocates the X-ray source 13, the electronic cassette 16, and the patientP at desired positions. Then, the operator presses the irradiationswitch 15 to drive the X-ray source 13 such that X-rays are emitted tothe patient P. In addition, the order of the setting of the imagingmenu, the setting of the irradiation conditions, and the positioning of,for example, the patient P may be reversed.

The imaging preparation command which is various kinds of informationincluding the imaging menu is received by the wireless communicationunit 22 or the wired communication unit 66 and is then received by thecontrol unit 54 (YES in Step ST110). After receiving the imagingpreparation command, the control unit 54 performs the AED operation.During the AED operation, as illustrated in FIG. 14, the power supplystate of the first to sixteenth ADCs 77 is periodically switched (StepST120, an irradiation start detection step).

The control unit 54 compares the dose signal DDS(C) obtained by the AEDoperation with the irradiation start determination threshold value (StepST130). With the emission of X-rays, the value of the dose signal DDS(C)increases. In a case in which the dose signal DDS(C) is greater than theirradiation start determination threshold value (YES in Step ST130), thecontrol unit 54 determines that the emission of X-rays has started (StepST140). The control unit 54 performs the pixel charge accumulationoperation (Step ST150). In a case in which the dose signal DDS(C) is notlarger than the irradiation start determination threshold value within apredetermined time (YES in Step ST160) and power is not turned off (NOin Step ST190), the control unit 54 returns to the standby operationagain (Step ST100).

In a case in which the control unit 54 detects the start of the emissionof X-rays, the timer starts the measurement of time. Until the timemeasured by the timer reaches the irradiation time in the irradiationconditions set by the console 17, the pixel charge accumulationoperation is continuously performed. In a case in which the timemeasured by the timer reaches the irradiation time in the irradiationconditions (YES in Step ST170), the control unit 54 performs the imagereading operation. During the image reading operation, as illustrated inFIG. 12, all of the first to sixteenth ADCs 77 are always in theoperating state (Step ST180, an image reading step). This series ofoperations is continuously performed until power is turned off (YES inStep ST190).

The image signal DIS(C) obtained by the image reading operation istransmitted as an X-ray image from the wireless communication unit 22 orthe wired communication unit 66 to the console 17. The X-ray image isdisplayed on the display 20 such that the operator browses the X-rayimage.

The number of ADCs 77 in the operating state per unit time T in the AEDoperation is less than that in the image reading operation by theswitching of the power supply state of the first to sixteenth ADCs 77.Therefore, it is possible to reduce the power consumption of the signalprocessing circuit 51 in the AED operation.

In the related art, even in the AED operation, the first to sixteenthADCs 77 are always in the operating state as in the image readingoperation and the number of ADCs 77 in the operating state per unit timeis equal to that in the image reading operation. Therefore, powerconsumption is significantly high in the AED operation whose operatingtime is longer than that of the image reading operation which ends in acase in which an X-ray image corresponding to one screen is read once.In particular, in the electronic cassette 16 driven by the battery 65,in a case in which power consumption is high, the battery 65 needs to becharged frequently. As a result, imaging efficiency is reduced.

However, in the first invention, it is possible to reduce the powerconsumption of the signal processing circuit 51 in the AED operation.Therefore, the battery 65 lasts longer than that in the related art. Asa result, the number of times the battery 65 is charged is reduced.Thus, it is possible to improve imaging efficiency.

A method that performs control such that a specific ADC 77 is always inthe non-operating state is considered as a method for reducing thenumber of operating ADCs 77 in the operating state per unit time T inthe AED operation to be less than that in the image reading operation.However, in a case in which a specific ADC 77 is always in thenon-operating state, the dose signal DDS(C) of the area AR that thespecific ADC 77 is in charge of is not read. That is, there is an areaAR that is not coverable by the AED operation.

In contrast, in this embodiment, as illustrated in FIG. 14, the powersupply state of all of the first to sixteenth ADCs 77 is periodicallyswitched to reduce the number of operating ADCs 77 in the operatingstate per unit time T in the AED operation so to be less than that inthe image reading operation. Therefore, it is possible to obtain theeffect of reading the dose signals DDS(C) from all of the areas AR1 toAR16 and covering all of the areas AR1 to AR16 in addition to the effectof reducing the power consumed of the signal processing circuit 51 inthe AED operation.

A method that performs control such that a specific ADC 77 is always inthe operating state and the other ADCs 77 are always in thenon-operating state is considered as another method for reducing thenumber of operating ADCs 77 in the operating state per unit time T inthe AED operation to be less than that in the image reading operation.However, in a case in which the power supply state is periodicallyswitched as in the first to sixteenth ADCs 77 according to thisembodiment, without performing control such that a specific ADC 77 isalways in the operating state, it is clear that the power consumption ofthe signal processing circuit 51 can be further reduced.

As can be seen from the above, the periodical switching of the powersupply state of at least one of a plurality of ADCs 77 in the AEDoperation is more effective than that in a case in which control isperformed such that a specific ADC 77 is always in the non-operatingstate or a case in which control is performed such that a specific ADC77 is always in the operating state and the other ADCs 77 are always inthe non-operating state.

Since all of the ADCs 77 are changed to the operating state in the imagereading operation, it is possible to obtain a high-quality X-ray image.

(1-2)-th Embodiment

In a (1-2)-th embodiment illustrated in FIG. 18, the control unit 54shifts the switching timing of the power supply state of all of thefirst to sixteenth ADCs 77. That is, first, the control unit 54 operatesthe first ADC 77 for the time T. Then, the control unit 54 operates thesecond ADC 77 for the time T and operates the third ADC 77 for the timeT. The control unit 54 continuously performs the switching of the powersupply state up to the sixteenth ADC 77. After operating the sixteenthADC 77 for the time T, the control unit 54 returns to the first ADC 77and operates the first ADC 77 for the time T again. Then, the controlunit 54 repeats the series of power supply state switching operations.

In this case, the reading period of the dose signal DDS(C) is 16T(=T′16) which is longer than 4T in the (1-1)-th embodiment. However,since the number of ADCs 77 in the operating state per unit time T is 1,the number of ADCs 77 per unit time T in the AED operation in a case inwhich 16 which is the number of ADCs 77 per unit time T in the imagereading operation is normalized to 1 is 1/16=0.0625, which is less than0.25 in the (1-1)-th embodiment.

(1-3)-th Embodiment

FIG. 19 illustrates a (1-3)-th embodiment. In the (1-1)-th embodiment,the example in which three ADCs 77 are disposed between two ADCs 77 inthe same group has been described. However, as in the (1-3)-thembodiment, there is no ADC 77 between two ADCs 77 in the same group. Inother words, two ADCs 77 in the same group may be adjacent to eachother.

In FIG. 19, each of the first and second ADCs 77, the third and fourthADCs 77, the fifth and sixth ADCs 77, the seventh and eighth ADCs 77, .. . , the thirteenth and fourteenth ADCs 77, and the fifteenth andsixteenth ADCs 77 form a group in which the power supply state isswitched at the same timing. However, there is no ADC 77 between twoADCs 77 belonging to the same group and the two ADCs 77 are adjacent toeach other.

(1-4)-th Embodiment

FIG. 20 illustrates a (1-4)-th embodiment. In each of theabove-described embodiments, the power supply state of the ADCs 77 isswitched in units of the areas AR. However, as in the (1-4)-thembodiment, the control unit 54 may switch the power supply state of theADCs 77 in units of the chips CP. Specifically, first, the control unit54 changes the first to fourth ADCs 77 in the chip CP1 to the operatingstate and changes them to the non-operating state after the lapse of thetime T. Then, similarly, the control unit 54 changes the fifth to eighthADCs 77 in the chip CP2 to the operating state and changes them to thenon-operating state after the lapse of the time T. Then, the controlunit 54 operates the ninth to twelfth ADCs 77 in the chip CP3 for thetime T and then operates the thirteenth to sixteenth ADCs 77 in the chipCP4 for the time T. Then, the control unit 54 repeats the series ofpower supply state switching operations.

As such, in a case in which the power supply state of the ADCs 77 isswitched in units of the chips CP, control is simpler than that in acase in which the power supply state is switched in units of the areasAR. In addition, it is possible to respond to the chip CP without afunction of switching the power supply state for each block BL.

(1-5)-th Embodiment

FIG. 21 illustrates a (1-5)-th embodiment. In each of theabove-described embodiments, the power supply state of all of the ADCs77 is periodically switched. However, the invention is not limitedthereto. As in the (1-5)-th embodiment, control may be performed suchthat at least one ADC 77 is always in the non-operating state.

As illustrated in FIG. 21, in the (1-5)-th embodiment, the control unit54 performs control such that the even-numbered ADCs 77, such as thesecond, fourth, sixth, . . . , sixteenth ADCs 77, are always in thenon-operating state during the AED operation. In contrast, the powersupply state of the odd-numbered ADCs 77, such as the first, third,fifth, . . . , fifteenth ADCs 77, is periodically switched as in each ofthe above-described embodiments. As such, there may be an ADC 77 that isalways in the non-operating state during the AED operation. In a case inwhich attention is focused on one ADC 77 and the ADC 77 is always in thenon-operating state, power consumption can be lower than that in a casein which the power supply state is periodically switched.

In contrast, there may be an ADC 77 that is always in the operatingstate during the AED operation as in the image reading operation (seeFIG. 27). However, in this case, at least one ADC 77 that is in thenon-operating state during the AED operation is required regardless ofwhether the power supply state is periodically switched or is fixed. Thereason is as follows. In a case in which all of the ADCs 77 are alwaysin the operating state, they are in the same state as that in the imagereading operation and the number of ADCs 77 in the operating state perunit time in the AED operation is not less than that in the imagereading operation.

(1-6)-th Embodiment

FIGS. 22 and 23 illustrate a (1-6)-th embodiment. In each of theabove-described embodiments, for example, as the first, fifth, ninth,and thirteenth ADCs 77 and the second, sixth, tenth, and fourteenth ADCs77 in the (1-1)-th embodiment illustrated in FIG. 14, at the timing whenone ADC 77 is switched from the operating state to the non-operatingstate, the other ADC 77 is switched from the non-operating state to theoperating state. However, the invention is not limited thereto. As inthe (1-6)-th embodiment, the timing when one ADC 77 is switched from theoperating state to the non-operating state may deviate from the timingwhen the other ADC 77 is switched from the non-operating state to theoperating state.

The (1-6)-th embodiment illustrated in FIG. 22 is the same as the(1-1)-th embodiment illustrated in FIG. 14 in that the first, fifth,ninth, and thirteenth ADCs 77, the second, sixth, tenth, and fourteenthADCs 77, the third, seventh, eleventh, and fifteenth ADCs 77, and thefourth, eighth, twelfth, and sixteenth ADCs 77 form groups in which thepower supply state is switched at the same timing. However, before oneADC 77 is switched from the operating state to the non-operating state,another ADC 77 is switched from the non-operating state to the operatingstate. For example, while the first, fifth, ninth, and thirteenth ADCs77 are in the operating state, the second, sixth, tenth, and fourteenthADCs 77 are switched to the operating state, specifically, at a timingT/2.

As such, since the timing when one ADC 77 is switched from the operatingstate to the non-operating state deviates from the timing when the otherADC 77 is switched from the non-operating state to the operating state,it is possible to reduce the reading period of the dose signal DDS(C).Specifically, while the reading period of the dose signal DDS(C) is 4Tin the (1-1)-th embodiment, the reading period is 2.5T in FIG. 22.Therefore, the reading period is reduced in this embodiment.

In this case, the number of ADCs 77 in the operating state per unit timeT is 6 (=4+(4′0.5)) since four ADCs 77 are in the operating state forthe time T and four ADCs 77 in the operating state for the time T/2.

FIG. 22 illustrates an example based on the (1-1)-th embodimentillustrated in FIG. 14. FIG. 23 illustrates an example based on the(1-2)-th embodiment illustrated in FIG. 18, in which the switchingtimings of the power supply state of all of first to sixteenth ADCs 77deviate from each other. In this case, similarly to the case illustratedin FIG. 22, before one ADC 77 is switched from the operating state tothe non-operating state, the other ADC 77 is switched from thenon-operating state to the operating state. For example, while the firstADC 77 is in the operating state, the second ADC 77 is switched to theoperating state, specifically, at a timing T/2. In this case, it is alsopossible to reduce the reading period of the dose signal DDS(C) from 16Tillustrated in FIG. 18 to 8.5T. In this case, the number of ADCs 77 inthe operating state per unit time T is 1.5.

(1-7)-th Embodiment

FIG. 24 illustrates a (1-7)-th embodiment. In each of theabove-described embodiments, the switching timings of the power supplystate of a plurality of ADCs 77 deviate from each other. However, in the(1-7)-th embodiment, the control unit 54 matches the switching timingsof the power supply state of all of the first to sixteenth ADCs 77.

In this case, the reading period of the dose signal DDS(C) is 2T whichis obtained by adding the first half time T for which all of the ADCs 77are in the operating state and the second half time T for which all ofthe ADCs 77 are in the non-operating state. In this case, the unit timeis not T, but is 2T. The number of ADCs 77 in the operating state perunit time 2T is 8 (=16/2) since all of 16 ADCs 77 are in the operatingstate for the first time T and no ADCs 77 are in the operating state forthe next time T.

(1-8)-th Embodiment

FIGS. 25 to 27 illustrate a (1-8)-th embodiment. In each of theabove-described embodiments, in the AED operation, the dose signalsDDS(C) based on the charge from all of the pixels 40 are read. That is,all of the pixels 40 function as detection pixels for reading the dosesignals DDS(C). However, instead of all of the pixels 40, some of aplurality of pixels 40 may be preset as the detection pixels.Hereinafter, a reference numeral is assigned to the detection pixel andthe detection pixel is referred to as a detection pixel 90 (see FIG.25). Hereinafter, the signal line 42 to which the detection pixel 90 isconnected is referred to as a detection channel 95 (see FIG. 25).

FIG. 25 illustrates an example in which all of the pixels 40 belongingto a total of eight areas AR from the area AR5 to the area AR12 that arecovered by the chips CP2 and CP3 among the chips CP1 to CP4 are set asthe detection pixels 90 (which are hatched). In this case, the detectionchannels 95 are the signal lines 42 which are connected to the fifth toeighth MUXs 76 in the chip CP2 and the ninth to twelfth MUXs 76 in thechip CP3.

For example, as illustrated in FIG. 26, during the AED operation, thecontrol unit 54 performs control such that the first to fourth ADCs 77of the chip CP1 and the thirteenth to sixteenth ADCs 77 of the chip CP4which are not in charge of the detection channels 95 are always in thenon-operating state. In addition, the control unit 54 periodicallyswitches the power supply state of the fifth to eighth ADCs 77 of thechip CP2 and the ninth to twelfth ADCs 77 of the chip CP3 which are incharge of the detection channels 95.

In a case in which the detection channel 95 is set, the ADC 77 which isnot in charge of the detection channel 95 is meaningless even though itis in the operating state in the AED operation. Therefore, the ADC 77 isalways in the non-operating state during the AED operation. On the otherhand, the power supply state of the ADC 77 which is in charge of thedetection channel 95 is periodically switched during the AED operation.The number of ADCs 77 in the operating state per unit time T is reducedby the above-mentioned configuration.

FIG. 27 is the same as FIG. 26 in that the ADC 77 which is not in chargeof the detection channel 95 is always in the non-operating state duringthe AED operation. However, in FIG. 27, the ADCs 77 (the fifth to eighthADCs 77 of the chip CP2 and the ninth to twelfth ADCs 77 of the chipCP3) which are in charge of the detection channels 95 are always in theoperating state. As can be seen from the example illustrated in FIG. 27,the first invention includes a case in which the power supply state ofthe ADC 77 is not periodically switched.

In FIG. 25, all of the signal lines 42 in the areas AR5 to AR12 are setas the detection channels 95. However, the detection channels 95 may beset by any method. For example, four consecutive detection channels 95may be set at intervals of 64 columns such that the first to fourthcolumns, the 65th to 68th columns, and the 129th to 132nd columns areset as the detection channels 95. In addition, the detection pixels 90may be set in one detection channel 95 by any method. For example, allof the pixels 40 corresponding to one column may not be set as thedetection pixels 90, but only the pixels 40 corresponding to the 481stto 960th rows that the third and fourth gate driving circuits 75 are incharge of may be set as the detection pixels 90.

(1-9)-th Embodiment

FIGS. 28 to 31 illustrate a (1-9)-th embodiment. In each of theabove-described embodiments, the pixel 40 for obtaining the image signalDIS(C) in the image reading operation is also used as the detectionpixel 90 for obtaining the dose signal DDS(C) in the AED operation.However, the invention is not limited thereto. A dedicated detectionpixel 90X specialized for the AED operation may be provided separatelyfrom the pixel 40 for detecting an X-ray image.

In a case in which the detection pixel 90X used only for the AEDoperation is provided, the pixels 40 and the detection pixels 90X aremixed on the light detection substrate 35. The light detection substrate35 is limited in size. Therefore, in a case in which an excessivelylarge number of detection pixels 90X are provided, a space for thepixels 40 is reduced and the quality of the X-ray image is degraded. Inaddition, the following is considered: in a case in which the detectionpixels 90X are provided so as to be concentrated on a region on thelight detection substrate 35, the region is not irradiated with X-raysdepending on the setting of the irradiation field. Therefore, forexample, as illustrated in FIG. 28, it is preferable that several tensto several hundreds of detection pixels 90X are provided with respect toseveral millions of pixels 40 and the detection pixels 90X aredispersively provided on the light detection substrate 35. For example,the number of detection pixels 90X provided in one detection channel 95is 12 among 2880 pixels.

A detection pixel 90X1 illustrated in FIG. 29 has the same basicconfiguration comprising the photoelectric conversion unit 43 and theTFT 44 as the pixel 40. Therefore, the detection pixel 90X1 can beformed by almost the same manufacturing process as the pixel 40. Thedetection pixel 90X1 is different from the pixel 40 in that the sourceelectrode and the drain electrode of the TFT 44 are short-circuited by ashort-circuit line 100. That is, in the detection pixel 90X1 illustratedin FIG. 29, the photoelectric conversion unit 43 is directly connectedto the signal line 42 by the short-circuit line 100. The signal line 42becomes the detection channel 95.

In the detection channel 95, the charge generated in the photoelectricconversion unit 43 of the detection pixel 90X1 flows out regardless ofthe on/off state of the TFT 44. Therefore, for example, even in a casein which the TFTs 44 of the pixels 40 in the same row are turned off andthe pixels 40 are in the pixel charge accumulation operation, the chargegenerated in the photoelectric conversion unit 43 of the detection pixel90X1 always flows into the CA 60 through the detection channel 95.

In this case, similarly to the (1-8)-th embodiment illustrated in FIGS.25 to 27, the ADC 77 that is not in charge of the detection channel 95is always in the non-operating state during the AED operation. Inaddition, the power supply state of the ADC 77 that is in charge of thedetection channel 95 is periodically switched or the ADC 77 is always inthe operating state during the AED operation.

As a short-circuited pixel in which the photoelectric conversion unit 43is directly connected to the signal line 42, a detection pixel 90X2illustrated in FIG. 30 which does not include the TFT 44 and includesonly the photoelectric conversion unit 43 may be used instead of thedetection pixel 90X1 illustrated in FIG. 29. In the examples illustratedin FIGS. 29 and 30, the charge generated in the detection pixel 90X1 or90X2 is always added to the charge generated in the pixel 40 in the samecolumn as the detection pixel 90X1 or 90X2 which is a short-circuitedpixel. As a result, it is difficult to use the pixel 40 in the samecolumn as the detection pixel 90X1 or 90X2 as a pixel for acquiring theimage signal DIS(C). Therefore, the pixel 40 and the detection pixel90X1 or 90X2 in the column corresponding to the detection channel 95 aretreated as defective pixels and are interpolated by the image signalsDIS(C) of the pixels 40 in the neighboring column that is not thedetection channel 95.

FIG. 31 illustrates an example in which a detection pixel 90X3 used onlyfor the AED operation is provided adjacent to a specific pixel 40. Thedetection pixel 90X3 comprises a photoelectric conversion unit 105 and aTFT 106 similarly to the pixel 40. A gate line 107 and a signal line(detection channel 95) different from the gate line 41 and the signalline 42 connected to the TFT 44 of the pixel 40 are connected to the TFT106. The gate line 107 is connected to a gate driving unit 108 thatperforms driving independently of the gate driving unit 50. Thedetection channel 95 is connected to the MUX unit 62 together with thesignal line 42.

During the AED operation, the gate driving unit 50 does not operate andonly the gate driving unit 108 operates. As in the (1-1)-th embodiment,the gate driving unit 108 applies the gate pulses to the gate lines 107corresponding to a plurality of rows at the same time to turn on theTFTs 106 connected to each gate line 107 in units of a plurality ofrows. Alternatively, the gate driving unit 108 may sequentially applythe gate pulses to each gate line 107.

In this case, similarly to the (1-8)-th embodiment illustrated in FIGS.25 to 27, the ADC 77 that is not in charge of the detection channel 95is always in the non-operating state during the AED operation. Inaddition, the power supply state of the ADC 77 that is in charge of thedetection channel 95 is periodically switched or the ADC 77 is always inthe operating state during the AED operation. The MUX unit 62 has thesame basic configuration as that in each of the above-describedembodiments except that it is connected not only to the signal line 42but also to the detection channel 95 connected to the detection pixel90X3. In addition, the detection channel 95 different from the signalline 42 may not be provided only for the detection pixel 90X3. The TFT106 of the detection pixel 90X3 may be connected to the signal line 42such that the signal line 42 is also used as the detection channel 95.

In the case of FIG. 31, the pixel 40 and the detection pixel 90X3 can bedriven independently by the gate driving units 50 and 108 and the signalline 42 and the detection channel 95 are separately provided. Therefore,as in FIGS. 29 and 30, the pixel 40 in the same column as the detectionpixel 90X3 may not be treated as the defective pixel.

(1-10)-th Embodiment

FIG. 32 illustrates a (1-10)-th embodiment. The (1-10)-th embodiment isconfigured such that the operator can set the detection pixels 90 fromwhich the dose signals DDS(C) are used to determine the start of theemission of X-rays among all of the detection pixels 90. For example, ina case in which the detection pixels 90X3 illustrated in FIG. 31 in the(1-9)-th embodiment are dispersively arranged on the light detectionsubstrate 35 illustrated in FIG. 28, in chest imaging, the detectionpixels 90X3 in a rectangular area LA1 corresponding to the lung field ofthe patient P are selected and the dose signals DDS(C) from the selecteddetection pixels 90X3 are used to determine the start of the emission ofX-rays as illustrated in FIG. 32. In contrast, in abdominal imaging, thedetection pixels 90X3 in a rectangular area LA2 are selected and thedose signals DDS(C) from the selected detection pixels 90X3 are used todetermine the start of the emission of X-rays.

In this case, the gate driving unit 108 has a function of selectivelyapplying the gate pulses to the TFTs 106 of the detection pixels 90X3 inthe areas LA1 and LA2. In a case in which the detection pixels 90X3 inthe area LA1 are selected in chest imaging, the signal lines 42 in arange RLA1 corresponding to the width of the area LA1 become thedetection channels 95. Therefore, control is performed such that thepower supply state of the ADCs 77 in charge of the range RLA1 isswitched or the ADCs 77 are always in the operating state during the AEDoperation. The ADCs 77 in charge of the other ranges RLA2 and RLA3 areswitched to the non-operating state. In contrast, in a case in which thedetection pixels 90X3 in the area LA2 are selected in abdominal imaging,control is performed such that the power supply state of the ADCs 77 incharge of the range RLA2 is switched or the ADCs 77 are always in theoperating state during the AED operation. In this case, the ADCs 77 incharge of the ranges RLA1 and RLA3 are switched to the non-operatingstate.

In FIG. 32, the detection pixel 90X3 illustrated in FIG. 31 in the(1-9)-th embodiment has been described as an example. However, theinvention is not limited thereto. In the configuration in which thepixel 40 for obtaining the image signal DIS(C) in the image readingoperation is also used as the detection pixel 90 for obtaining the dosesignal DDS(C) in the AED operation as in the (1-8)-th embodimentillustrated in FIGS. 25 to 27, in a case in which the function ofselectively applying the gate pulses G(R) to the TFTs 44 of the pixels40 in a specific area is provided in the gate driving unit 50, the sameeffect as described above can be obtained.

For the detection pixels 90X1 and 90X2 illustrated in FIGS. 29 and 30 inthe (1-9)-th embodiment, in a case in which the detection pixels 90X1and 90X2 are arranged only in the area LA1 in the range RLA1 and arearranged only in the area LA2 in the range RLA2, the same effect asdescribed above can be obtained.

(1-11)-th Embodiment

FIGS. 33 and 34 illustrate a (1-11)-th embodiment. As described above,the dose signal DDS(C) obtained by the AED operation is not used as theimage information of the patient P. Therefore, the accuracy required forthe image signal DIS(C) output in the image reading operation is notrequired for the dose signal DDS (C) in the AED operation. In the(1-11)-th embodiment illustrated in FIG. 33, the operation of the CDS 61in the AED operation is simpler than that in the image reading operationto further reduce the power consumption of the signal processing circuit51 in the AED operation.

FIG. 33A is a flowchart illustrating the operation of the CDS 61 in theimage reading operation which has been described in brief with referenceto FIG. 6. That is, the first S/H 73A of the CDS 61 holds a reset noisecomponent (Step ST300). Then, the second S/H 73B holds an analog voltagesignal V(C) (Step ST310). Finally, the difference amplifier 74calculates the difference between the reset noise component and theanalog voltage signal V(C) held in the first and second S/Hs 73A and 73Band outputs an analog voltage signal V(C) from which noise has beenremoved (Step ST320).

In contrast, in the AED operation, the holding of the reset noisecomponent by the first S/H 73A in Step ST300 is skipped and the processstarts from the holding of the analog voltage signal V(C) by the secondS/H 73B in Step ST310 as illustrated in FIG. 33B. Then, the differenceamplifier 74 outputs the analog voltage signal V(C) without calculatingthe difference between the reset noise component and the analog voltagesignal V(C) (Step ST330).

As such, in the AED operation, since the holding of the reset noisecomponent by the first S/H 73A is skipped, the supply of power to thefirst S/H 73A is not necessary or it is possible to drive the first S/H73A with power lower than that in the image reading operation.Therefore, it is possible to further reduce the power consumption of thesignal processing circuit 51 in the AED operation. In addition, in theAED operation, it is possible to output the analog voltage signal V(C)at a higher speed than that in the image reading operation by a valuecorresponding to the operation of skipping the holding of the resetnoise component by the first S/H 73A.

In the (1-1)-th embodiment, the example in which the differenceamplifier 74 is connected to the input terminal of the MUX 76 asillustrated in FIG. 6 has been described. However, the invention is notlimited thereto. As illustrated in FIG. 34, two MUXs 76A and 76B may beconnected between the first and second S/Hs 73A and 73B and thedifference amplifier 74 and the difference amplifier 74 may be connectedbetween the MUXs 76A and 76B and the ADC 77.

In this case, for example, the first and second S/Hs 73A and 73B of aplurality of CDSs 61 corresponding to the columns in the same area ARare connected to the MUXs 76A and 76B, respectively. In the (1-1)-thembodiment, as illustrated in FIG. 6, since the difference amplifier 74is connected to a stage behind the MUX 76, the difference amplifier 74is provided for each CDS 61. However, in FIG. 34, since the differenceamplifier 74 is connected to a stage behind the MUXs 76A and 76B, thenumber of difference amplifiers 74 is equal to the number of ADCs 77.

In the configuration illustrated in FIG. 34, as illustrated in FIG. 33B,the holding of the reset noise component by the first S/H 73A in the AEDoperation is skipped. Therefore, it is possible to reduce powerconsumption. In this case, it is possible to reduce the supply of powerto the MUX 76A in addition to the first S/H 73A. In addition, the numberof difference amplifiers 74 is reduced to reduce the supply of power tothe difference amplifier 74. Therefore, it is possible to further reducethe power consumption of the signal processing circuit 51 in the AEDoperation.

(1-12)-th Embodiment

FIGS. 35 to 37 illustrate a (1-12)-th embodiment. Here, for example,FIG. 35 illustrates a temperature distribution in the column directionof the block BL7 in a case in which the sixth and eighth ADCs 77adjacent to the seventh ADC 77 illustrated in FIG. 18 in the (1-2)-thembodiment is in the non-operating state for a relatively long time, thepower supply state is switched at different timings, and the seven theseventh ADC 77 is in the operating state. That is, the temperaturedistribution has a mountain shape in which the temperature drops at bothends due to the influence of the adjacent blocks BL6 and BL8 in thenon-operating state and the temperature in a central portion is higherthan that at both ends. The reason why the temperature distribution ofthe block BL6 has a gentle mountain shape is that, as illustrated inFIG. 18, the sixth ADC 77 is in the operating state immediately beforethe seventh ADC 77 changes to the operating state.

In a case in which the block BL is in charge of a large number ofcolumns of the pixels 40, the width of the block BL in the columndirection is large. Therefore, for a change in the temperaturedistribution in the block BL, the central portion is approximately flatand becomes gentle. In contrast, in a case in which the block BL is incharge of a small number of columns of the pixels 40, the width of theblock BL in the column direction is small. Therefore, the change in thetemperature distribution is steep. In a case in which there is a bias inthe temperature distribution in the block BL, a temperature drift occursin the digital signal DS(C). It is preferable to arrange the detectionchannel 95 having the detection pixels 90 in a central portion of thearea AR in which a temperature gradient is likely to be relatively flat,in order to minimize the influence of the temperature drift.

In the examples illustrated in FIGS. 29 and 30 in the (1-9)-thembodiment, the number of detection pixels 90X1 or 90X2 arranged in onedetection channel 95 is less than 1% of the total number of pixels. Forexample, among 2880 pixels, 12 pixels are the detection pixels. As such,the following relationship is established between the number of pixels40 and the number of detection pixels 90X1 or 90X2: the number of pixels40»the number of detection pixels 90X1 or 90X2.

Here, even in a case in which the TFT 44 is in an off state, a verysmall amount of charge generated in the pixel 40 flows into the signalline 42. The charge is referred to as a leak charge. As schematicallyillustrated in FIG. 36, in addition to charge SC generated in thedetection pixel 90X1 or 90X2, the leak charge LC flows into thedetection channel 95 in the examples illustrated in FIGS. 29 and 30.Since the leak charge LC is added to the charge SC generated in thedetection pixel 90X1 or 90X2 which is desired to be originally extractedas the dose signal DDS(C), it becomes noise in a case in which the startof the emission of X-rays is determined. In addition, since the numberof pixels 40»the number of detection pixels 90X1 or 90X2 is satisfied,the amount of leak charge LC is not negligible with respect to theamount of charge SC generated in the detection pixel 90X1 or 90X2. As aresult, the risk of erroneously determining the start of the emission ofX-rays increases. In the (1-12)-th embodiment, correction which removesthe influence of the leak charge LC from the dose signal DDS(C) of thedetection channel 95 and then removes the influence of the temperaturedrift is performed.

Specifically, as illustrated in FIG. 37, the columns of only the pixels40 without including the detection pixel 90X1 or 90X2 are providedadjacent to the detection channel 95 having the detection pixels 90X1 or90X2 arranged therein such that the detection channel 95 is interposedtherebetween. Hereinafter, the signal line 42 corresponding to thecolumn of only the pixels 40 without including the detection pixel 90X1or 90X2 is referred to as a reference channel 120.

In FIG. 37, the detection channel 95 and the reference channel 120 areconnected to the same MUX 76 and the same ADC 77. That is, the detectionchannel 95 and the reference channel 120 are in the same block BL. Inthis case, the control unit 54 changes the ADC 77 that is in charge ofboth the detection channel 95 and the reference channel 120 to theoperating state during the AED operation. In a case in which thedetection channel 95 and the reference channel 120 are divided intodifferent blocks BL and are connected to different ADCs 77, the controlunit 54 changes the ADC 77 that is in charge of the detection channel 95to the operating state and changes the ADC 77 that is in charge of thereference channel 120 to the operating state.

Then, the ADC 77 outputs the dose signal DDS(C) based on the analogvoltage signal V(C) from the detection channel 95 and the dose signalsDDS(C−1) and DDS(C+1) based on the analog voltage signals V(C−1) andV(C+1) from the reference channel 120 to the memory 52. Hereinafter, thedose signals DDS(C−1) and DDS(C+1) are referred to as reference signalsDRS(C−1) and DRS(C+1), respectively.

A leak charge correction unit 121 accesses the memory 52 and reads thedose signal DDS(C) from the memory 52. The leak charge correction unit121 is provided in, for example, the control unit 54. The leak chargecorrection unit 121 performs subtraction represented by the followingExpression (1) to obtain a leak charge corrected dose signal RCDDS(C)from the dose signal DDS(C):RCDDS(C)=DDS(C)−DRS(C)  (1)(where DRS(C)={DRS(C−1)+DRS(C+1)}/2). That is, the leak charge correcteddose signal RCDDS(C) is obtained by subtracting DRS(C), which is theaverage value of two reference signals DRS(C−1) and DRS(C+1) from thereference channels 120 corresponding to two columns, from the dosesignal DDS(C) from the detection channel 95.

The reference signals DRS(C−1) and DRS(C+1) are components based on theleak charge LC of the pixels 40 connected to the reference channels 120.It is considered that the average value DRS(C) of the reference signalsDRS(C−1) and DRS(C+1) is substantially matched with the component basedon the leak charge LC of the pixels 40 connected to the detectionchannel 95 since the detection channel 95 and the reference channel 120are adjacent to each other and include almost the same number of pixels40. Therefore, the subtraction represented by Expression (1) isperformed to remove the component of the leak charge LC from the dosesignal DDS(C).

A temperature drift correction unit 122 is provided in a stage behindthe leak charge correction unit 121. The temperature drift correctionunit 122 is provided in, for example, the control unit 54 similarly tothe leak charge correction unit 121. The temperature drift correctionunit 122 multiplies the leak charge corrected dose signal RCDDS(C) by acorrection coefficient α(C) to calculate a temperature drift correcteddose signal DRCDDS(C) as illustrated in the following Expression (2):DRCDDS(C)=RCDDS(C)×α(C)  (2).

The temperature distribution, which is illustrated in FIG. 35, in thesignal processing circuit 51 including the detection channel 95 and thereference channel 120 is reflected in the reference signals DRS(C−1) andDRS(C+1). That is, the degree of the temperature drift occurring in thedose signal DDS(C) is known from the reference signals DRS(C−1) andDRS(C+1). The correction coefficient α(C) is calculated from acalculation formula F{DRS(C−1), DRS(C+1)} having the reference signalsDRS(C−1) and DRS(C+1) as variables. The correction coefficient α(C) isused such that the value of the leak charge corrected dose signalRCDDS(C) is equal to that in a case in which the leak charge correcteddose signal RCDDS(C) is read in a standard state in which all of theADCs 77 are in the operating state in the image reading operation andeach block BL1-16 is in a thermal equilibrium state. The correctioncoefficient α(C) is calculated for each detection channel 95. Inaddition, the correction coefficient α(C) may be calculated from acalculation formula having the average value DRS(C) of the referencesignals DRS(C−1) and DRS(C+1) as a variable.

A temperature measurement function of measuring the temperature TP of acentral portion of each block BL is provided in some chips CP inadvance. In this case, the correction coefficient α(C) is calculated onthe basis of the temperature TP acquired by the temperature measurementfunction (using a calculation formula having the temperature TP as avariable). In a case in which the temperature measurement function isnot provided in the chip CP, the temperature measurement function may beseparately provided to acquire the temperature TP.

The correction of the temperature drift by the temperature driftcorrection unit 122 may not be performed in a case in which it isdetermined that there is no temperature drift in the dose signal DDS(C)such as a case in which the temperature TP is in the standard state.Specifically, a threshold value is set to the temperature TP. In a casein which the temperature TP is equal to or less than the thresholdvalue, the temperature drift is not corrected. In a case in which thetemperature TP is greater than the threshold value, the temperaturedrift is corrected.

In the image reading operation, since all of the ADCs 77 are always inthe operating state, the bias in the temperature distributionillustrated in FIG. 35 is less likely to occur. Of course, thetemperature drift correction unit 122 may also perform temperature driftcorrection for the image signal DIS(C).

In a case in which the power supply state of the ADCs 77 is switched inunits of the chips CP as in the (1-4)-th embodiment illustrated in FIG.20, the bias in the temperature distribution illustrated in FIG. 35 doesnot occur in units of the blocks BL, but occurs in units of the chipsCP. In this case, the temperature TP is measured in units of the chipsCP and the temperature drift is corrected in units of the chips CP.

In a case in which the power supply state of the ADCs 77 is switched inunits of the chips CP, it is preferable to take measures to prevent thetemperature distribution from being biased, for example, measures toconnect adjacent chips CP with a thermally conducting member, such as aheat sink or a heat pipe.

In FIG. 37, one reference channel 120 is provided on each side of thedetection channel 95, that is, a total of two reference channels 120 areprovided adjacent to each other with the detection channel 95 interposedtherebetween. However, a plurality of reference channels 120 may beprovided on each side of the detection channel 95. It is preferable thatthe number of reference channels 120 provided on each side is equal toor greater than 2, that is, the total number of reference channels 120is equal to or greater than 4. The reason is that, in a case in whichthe number of reference channels 120 is small, the number of referencesignals is small, and there is a variation in the value of the referencesignal value in each reference channel 120, the reliability of theaverage value DRS(C) of the reference signals subtracted from the dosesignal DDS(C) is reduced.

In the case of the detection pixel 90X3 illustrated in FIG. 31 in the(1-9)-th embodiment, the signal line 42 and the detection channel 95 areseparately provided and the pixel 40 is not connected to the detectionchannel 95. Therefore, there is no concern that the leak charge LC ofthe pixel 40 will flow into the detection channel 95. In a case in whichthe detection channel 95 is also used as the signal line 42 in FIG. 31and the TFT 106 is turned off, the charge generated in the detectionpixel 90X3 does not flow into the signal line 42. Therefore, in a casein which the TFT 106 is in the off state, the signal line 42 that isalso used as the detection channel 95 acts just like the referencechannel 120. Therefore, in this case, the digital signal DS(C) read in astate in which the TFT 106 is turned off may be replaced with areference signal and the reference signal may be subtracted from thedose signal DDS(C) read in a state in which the TFT 106 is turned on.That is, in any case illustrated in FIG. 31, it is not necessary toprovide a dedicated reference channel 120.

(1-13)-th Embodiment

In a (1-13)-th embodiment illustrated in FIG. 38, in the AED operation,the control unit 54 switches an interface (hereinafter, referred to asan I/F) that transmits the digital signal DS(C) in a stage behind theADC 77 to one having a lower power consumption than that in the imagereading operation. In this configuration, the power consumption of thesignal processing circuit 51 in the AED operation may be reduced.

In FIG. 38, two types of interfaces, that is, a low voltage differentialsignaling (LVDS) I/F 125 and a CMOS I/F 126 are prepared as the I/F fortransmitting the digital signal DS(C) between the ADC 77 and the memory52. The LVDS I/F 125 has a higher transmission accuracy than the CMOSI/F 126, but has a higher power consumption than the CMOS I/F 126. Thecontrol unit 54 controls the operation of a switch 127 to switch thetransmission I/Fs.

FIG. 38A illustrates a case in which the AED operation is performed andFIG. 38B a case in which the image reading operation is performed. Thatis, the CMOS I/F 126 is selected in the AED operation and the LVDS I/F125 is selected in the image reading operation.

As such, since the CMOS I/F 126 is selected in the AED operation, it ispossible to further reduce the power consumption of the signalprocessing circuit 51 in the AED operation. The accuracy of thetransmission of the dose signal DDS(C) is low. However, since the dosesignal DDS(C) is not used as the image information of the patient P,some errors in transmission do not cause a big problem. On the otherhand, since the LVDS I/F 125 is selected in the image reading operation,power consumption increases, but it is possible to accurately transmitthe image signal DIS(C) to the memory 52.

In addition, only the CMOS I/F 126 may be provided as the transmissionI/F for the digital signal DS(C) between the ADC 77 and the memory 52and the supply voltage to the CMOS I/F 126 may be switched. For example,the supply voltage is 5.0 V in the image reading operation and is 3.3 Vin the AED operation. Alternatively, the supply voltage may be 2.5 V inthe image reading operation and may be 1.8 V in the AED operation. Asthe supply voltage becomes higher, the dynamic range becomes wider andthe accuracy of transmission becomes higher. However, power consumptionbecomes higher. Therefore, in the AED operation, the supply voltage isswitched to a lower voltage than that in the image reading operation. Asa result, it is possible to further reduce the power consumption of thesignal processing circuit 51 in the AED operation.

In each of the above-described embodiments, the second state has beendescribed as the non-operating state. As described above, thenon-operating state includes the state in which the power PSL_A issupplied, the power-off state in which no power is supplied to the ADC77, and the state in which the supply of the clock signal to the ADC 77is stopped. However, the second state is not limited to thenon-operating state. For example, the second state may be a state inwhich the number of pulses per unit time in the clock signal supplied tothe ADC 77 is less than that in the first state and the powerconsumption of the ADC 77 per unit time is less than that in the firststate.

2. Second Invention

In a second invention illustrated in FIGS. 39 to 43 which will bedescribed below, the control unit 54 changes at least one of thenon-detection CAs 131 (see FIG. 39A) which are the CAs 60 connected tothe non-detection channels 130 (see FIG. 39A) as the signal lines 42other than the detection channels 95 among a plurality of CAs 60 to apower saving state in which power supplied to the non-detection CAs 60in the AED operation is lower than normal power in the image readingoperation. Therefore, the power supplied to the CAs 60 including thenon-detection CA 131 in the AED operation is lower than that in theimage reading operation.

In the second invention, for example, the X-ray imaging system 10 andthe electronic cassette 16 have the same basic configuration as those inthe first invention. In addition, the patterns described in the (1-1)-thto (1-7)-th embodiments can be applied to the switching pattern of thepower supply state of the ADC 77. Further, the second invention may becombined with other embodiments (the (1-8)-th to (1-13)-th embodiments)of the first invention. Hereinafter, the same components as those in thefirst invention are denoted by the same reference numerals and thedescription thereof will not be repeated. The difference from the firstinvention will be mainly described.

(2-1)-th Embodiment

FIGS. 39 and 40 illustrate a (2-1)-th embodiment. In the (2-1)-thembodiment, for example, a configuration including the detection pixel90X1 illustrated in FIG. 29 or the detection pixel 90X2 illustrated inFIG. 30 in the (1-9)-th embodiment will be described. However, theconfiguration is not limited thereto.

In the (2-1)-th embodiment, FIG. 39A illustrates a case in whichodd-numbered columns, such as the first, third, fifth, . . . , 143rdcolumns, are the detection channels 95 and the even-numbered columns,the second, fourth, sixth, . . . , 144th columns, are the non-detectionchannels 130 for simplicity of explanation. Hereinafter, the CA 60connected to the detection channel 95 is referred to as a detection CA132 in order to distinguish the CA 60 from the non-detection CA 131which is the CA 60 connected to the non-detection channel 130. Inaddition, alphabets DT above the detection channel 95 indicate that thecolumn is the detection channel 95 and alphabets NDT above thenon-detection channel 130 indicate that the column is the non-detectionchannel 130.

The MUX 76 sequentially selects the analog voltage signals V(C) from aplurality of CAs 60 and outputs the selected analog voltage signal V(C)to the ADC 77 as in each of the above-described embodiments.

In the (2-1)-th embodiment, as illustrated in FIG. 39B, it is assumedthat the power P_C supplied to the CA 60 in the AED operation is PN_C inthe case of the detection CA 132 and is PL_C lower than PN_C in the caseof the non-detection CA 131. The supply power PN_C is power supplied toall of the CAs 60 in the image reading operation and corresponds tonormal power. The power PL_C supplied to the non-detection CA 131 is,for example, about 1/10 of the normal power PN_C. That is, the state ofthe non-detection CA 131 illustrated in FIG. 39B is a low power state inwhich the power PL_C that is lower than the normal power PN_C and isgreater than 0 is supplied.

As such, since only the power PL_C lower than the normal power PN_C issupplied to the non-detection CA 131, the digital signal DS(C) based onthe analog voltage signal V(C) from the non-detection CA 131 has ameaningless value in terms of data. Therefore, as illustrated in FIG.39A, the control unit 54 discards the digital signal DS(C) based on theanalog voltage signal V(C) from the non-detection CA 131, without usingit as the dose signal DDS(C).

FIG. 40 is a flowchart illustrating the procedure of the operation ofthe electronic cassette according to the (2-1)-th embodiment. Theflowchart differs from the flowchart illustrated in FIG. 17 in the(1-1)-th embodiment in Step ST1202 and Step ST1802 surrounded by aone-dot chain line. Hereinafter, only the difference will be described.

In Step ST1202, in the AED operation, the power supplied to thedetection CA 132 is set to the normal power PN_C and the power suppliedto the non-detection CA 131 is set to PL_C lower than PN_C (irradiationstart detection step). In Step ST1802, in the image reading operation,the power supplied to all of the CAs 60 is set to the normal power PN_Cwithout distinguishing between the detection CA 132 and thenon-detection CA 131 (image reading step).

As such, since the non-detection CA 131 is in the power saving state inwhich the power supplied to the non-detection CA 131 in the AEDoperation is lower than the normal power, it is possible to reduce thepower consumption of the signal processing circuit 51 in the AEDoperation. Therefore, similarly to the first invention, the battery 65lasts longer than that in the related art and thus the number of timesthe battery 65 is charged is reduced. Therefore, it is possible toimprove imaging efficiency.

The non-detection CA 131 that is in the power saving state in the AEDoperation may be at least one of the non-detection CAs 131. Of course,it is preferable that all of the non-detection CAs 131 are changed tothe power saving state in order to obtain the maximum effect.

(2-2)-th Embodiment

FIG. 41 illustrates a (2-2)-th embodiment. In the (2-1)-th embodimentillustrated in FIGS. 39 and 40, the power PL_C supplied to thenon-detection CA 131 in the AED operation is a value less than 0.However, in the (2-2)-th embodiment, as illustrated in FIG. 41, thepower PL_C supplied to the non-detection CA 131 in the AED operation is0. That is, the non-detection CA 131 is a power-off state in which thesupply of power is stopped.

As such, in a case in which the non-detection CA 131 is in the power-offstate, the power supplied to the non-detection CA 131 is 0. Therefore,it is possible to further reduce the power consumption of thenon-detection CA 131 as compared to the (2-1)-th embodiment illustratedin FIGS. 39 and 40.

However, in a case in which the non-detection CA 131 is in the power-offstate, a virtual short state between two input terminals of thenon-detection CA 131 is not maintained and the potential of the inputstage of the non-detection CA 131 becomes indefinite. Therefore, thecharge of the non-detection channel 130 also becomes unstable, which hasa bad influence on the image reading operation later. For this reason,it is preferable to supply the power PL_C that does not cause thepotential of the input stage of the non-detection CA 131 to beindefinite to change the non-detection CA 131 to a low power state as inthe (2-1)-th embodiment rather than to set the power supplied to thenon-detection CA 131 to 0 to change the non-detection CA 131 to thepower-off state as in the (2-2)-th embodiment.

In a case in which the non-detection CA 131 is in the power-off state, ameasure illustrated in FIG. 42 may be taken in order to prevent a badinfluence on the image reading operation. That is, a switch 133 that isturned on and off under the control of the control unit 54 is providedin a stage before the non-detection CA 131. Then, the control unit 54turns off the switch 133 to disconnect the non-detection CA 131 from thenon-detection channel 130 in the AED operation illustrated in FIG. 41Ain which no power is supplied. In addition, the control unit 54 appliesa reference potential, which is the same as that in a case in which thenormal power PN_C is supplied, to the non-detection CA 131. In contrast,the control unit 54 turns on the switch 133 in the image readingoperation illustrated in FIG. 41B in which the normal power PN_C issupplied. According to this configuration, it takes a lot of time andeffort to provide the switch 133, but the instability of the charge ofthe non-detection channel 130 caused by the indefinite potential of theinput stage of the non-detection CA 131 does not has an influence on theimage reading operation.

In this case, similarly to the (2-1)-th embodiment, the non-detection CA131 that is in the power-off state in the AED operation may be at leastone of the non-detection CAs 131. It is preferable that all of thenon-detection CAs 131 are in the power-off state in order to reducepower consumption.

(2-3)-th Embodiment

In a (2-3)-th embodiment illustrated in FIG. 43, in addition to thenon-detection CA 131, the detection CA 132 is driven in a low powerstate in which power lower than the normal power PN_C and is greaterthan 0 is supplied. Specifically, the power supplied to thenon-detection CA 131 in the AED operation is PL_C1 that is 1/10 of thenormal power PN_C and the power supplied to the detection CA 132 isPL_C2 that is ½ of the normal power PN_C. The transient responsecharacteristic of the detection CA 132 is reduced in correspondence to ½of the normal power PN_C. In this case, the operation speed of the ADC77 is delayed so as to be matched with the reduction in the transientresponse characteristic. This configuration does not cause any problembecause the dose signal DDS(C) that is meaningful in terms of data isobtained. Since the power supplied to the detection CA 132 in additionto the non-detection CA 131 is reduced, it is possible to further reducethe power consumption of the signal processing circuit 51 in the AEDoperation.

In the (2-3)-th embodiment, similarly to the non-detection CA 131according to each of the above-described embodiments, the detection CA132 that is in the low power state in the AED operation may be at leastone of the detection CAs 132. It is preferable that all of the detectionCAs 132 are in the low power state in order to reduce power consumption.

As described above, each embodiment of the second invention may becombined with each embodiment of the first invention. For example, asillustrated in FIG. 14 of the (1-1)-th embodiment, the control unit 54may periodically switch the power supply state of the ADC 77 and the MUX76 which form the block BL from the first state to the second state. Inthis case, the first state is, for example, the operating state and is astate in which power required to fulfill the functions of each of theMUX 76 and the ADC 77 is supplied to each of the MUX 76 and the ADC 77.In contrast, the second state is, for example, the non-operating stateand is a state in which power incapable of fulfilling the functions issupplied to at least one of the MUX 76 or the ADC 77 or a state in whichno clock signal is applied to the ADC 77. Further, the second stateincludes a state in which the number of pulses per unit time in theclock signal applied to the ADC 77 is less than that in the first state.

For example, the switching patterns of power supply to the ADC 77 andthe block BL in the second invention and the first invention may becombined as follows. First, in a case in which there are two or moreblocks BL including the MUX 76 and the ADC 77 whose power supply stateis periodically switched as illustrated in, for example, FIG. 14 of the(1-1)-th embodiment, the control unit 54 may shift the switching timingof the power supply state of at least two of the two or more blocks BL.

In addition, the control unit 54 may shift the switching timing of thepower supply state for each of a plurality of groups to which two ormore blocks BL belong, as illustrated in, for example, FIG. 14 of the(1-1)-th embodiment. In this case, it is preferable that at least oneblock BL is disposed between two blocks BL belonging to the same group.Alternatively, as illustrated in, for example, FIG. 18 of the (1-2)-thembodiment, the switching timing of the power supply state of all of thetwo or more blocks BL may be shifted.

As illustrated in, for example, FIG. 21 of the (1-5)-th embodiment, in acase in which there are a plurality of blocks BL including the MUX 76 towhich only the non-detection CA 131 is connected, at least one of theplurality of blocks BL may be always in the second state.

As in the (1-12)-th embodiment illustrated in FIGS. 35 to 37, leakcharge correction and temperature drift correction may be performed forthe dose signal DDS(C).

In addition, the (1-8)-th embodiment illustrated in FIGS. 25 to 27 inwhich the detection channel 95 that is the signal line 42 to which thedetection pixel 90 used for the AED operation is connected is set, the(1-9)-th embodiment illustrated in FIGS. 28 to 31 in which the detectionpixel 90X used only for the AED operation is provided, the (1-10)-thembodiment illustrated in FIG. 32 in which the setting of the detectionpixel 90 can be changed, the (1-11)-th embodiment illustrated in FIGS.33 and 34 in which the operation of the CDS 61 in the AED operation issimplified, and the (1-13)-th embodiment illustrated in FIG. 38 in whichthe digital signal transmission I/F is switched may be combined witheach other.

3. Third Invention

In a third invention illustrated in FIGS. 44 to 49 which will bedescribed below, the control unit 54 selectively outputs the analogvoltage signals V(C) from some CAs including the detection CA 132 to theADC 77, directs the ADC 77 to perform only an AD conversion process forthe selectively output analog voltage signal V(C), and reduces thenumber of pulses per unit time in the clock signal of the ADC 77 in theAED operation to be less than that in the image reading operation.

In the third invention, similarly to the second invention, for example,the X-ray imaging system 10 and the electronic cassette 16 have the samebasic configuration as those in the first invention. In addition, thepatterns described in the (1-1)-th to (1-7)-th embodiments can beapplied to the switching pattern of the power supply state of the ADC77. Further, the third invention may be combined with other embodiments(the (1-8)-th to (1-13)-th embodiments) of the first invention and the(2-1)-th to (2-3)-th embodiments of the second invention. Hereinafter,the same components as those in the first and second inventions aredenoted by the same reference numerals and the description thereof willnot be repeated. The difference from the first and second inventionswill be mainly described.

(3-1)-th Embodiment

FIGS. 44 to 48 illustrate a (3-1)-th embodiment. In the (3-1)-thembodiment, similarly to the (2-1)-th embodiment, for example, aconfiguration including the detection pixel 90X1 illustrated in FIG. 29or the detection pixel 90X2 illustrated in FIG. 30 in the (1-9)-thembodiment will be described. However, the configuration is not limitedthereto.

FIG. 44 illustrates the procedure of reading the dose signals DDS(C) inthe area AR1 including the first to 144th columns as in FIG. 9. FIG. 44illustrates a case in which odd-numbered columns, such as the first,third, fifth, . . . , 143rd columns, are the detection channels 95 andthe even-numbered columns, the second, fourth, sixth, . . . , 144thcolumns, are the non-detection channels 130 as in FIG. 39A.

In this case, the difference from FIG. 39A is that the MUX 76 is changedto a MUX 135. The MUX 76 has only the function of sequentially selectingthe columns one by one. In contrast, the MUX 135 has a function ofskipping the non-detection channels 130 corresponding to theeven-numbered columns and sequentially selecting the analog voltagesignals V(C) from the detection CAs 132 of the detection channels 95corresponding to the odd-numbered columns. That is, the MUX 135 has afunction of selecting the analog voltage signal V(C) from some of aplurality of connected CAs 60, in this case, the detection CAs 132 ofthe detection channels 95. For example, this function can be implementedby providing a switch in a flip-flop circuit of a shift register formingthe MUX 135.

In the procedure of reading the dose signal DDS(C), first, asillustrated in (A) of FIG. 44, the first MUX 135 selects an analogvoltage signal V(1) corresponding to the first column. Then, the analogvoltage signal V(1) is input to the first ADC 77 and the first ADC 77converts the analog voltage signal V(1) into a dose signal DDS(1). Then,as illustrated in (B) of FIG. 44, an analog voltage signal V(2)corresponding to the second column is skipped and the first MUX 135selects an analog voltage signal V(3) corresponding to the third column.Then, the analog voltage signal V(3) is input to the first ADC 77 andthe first ADC 77 converts the analog voltage signal V(3) into a dosesignal DDS(3). Then, as illustrated in (C) of FIG. 44, the first MUX 135selects an analog voltage signal V(5) corresponding to the fifth column.Then, the analog voltage signal V(5) is input to the first ADC 77 andthe first ADC 77 converts the analog voltage signal V(5) into a dosesignal DDS(5).

This series of operations are repeated by the first MUX 76 and the firstADC 77. Finally, as illustrated in (D) of FIG. 44, an analog voltagesignal V(143) corresponding to the 143rd column is converted into a dosesignal DDS(143). Then, the reading of the dose signals DDS(1), DDS(3),DDS(5), . . . , DDS(143) in the area AR1 ends. This holds for each MUX135 and each ADC 77 in the other areas AR2 to AR16.

As such, while the image signals DIS(C) corresponding to all columns areread in the image reading operation, only the dose signals DDS(C)corresponding to the odd-numbered columns are selectively read in theAED operation. Therefore, in the AED operation, the number of digitalsignals DS(C) that need to be read at the same time is ½ of that in theimage reading operation. In the AED operation, in a case in which thedose signals DDS(C) whose number has been reduced by half are read atthe same time as those in the image reading operation that reads theimage signals DIS(C) corresponding to all of the columns, it is possibleto reduce the operation speed of the ADC 77 by a value corresponding tothe reduction in the reading time.

Specifically, as illustrated in FIG. 45, the number of pulses NPU_A perunit time in the clock signal of the ADC 77 is NPUN_A which is thenormal number of pulses in the image reading operation and is NPUL_Athat is ½ of NPUN_A in the AED operation.

There are two methods for setting the number of pulses per unit time inthe clock signal of the ADC 77 to NPUL_A that is ½ of NPUN_A in theimage reading operation. FIG. 46 illustrates the first method. (A) ofFIG. 46 illustrates a clock signal CLN_A in the image reading operationand (B) of FIG. 46 illustrates a clock signal CLL_A in the AEDoperation.

In FIG. 46, for the period TC of the clock signal, the period of theclock signal CLN_A in the image reading operation is equal to the periodof the clock signal CLL_A in the AED operation. The clock signal CLN_Ais continuously generated without intermission, regardless of thedetection channel 95 and the non-detection channel 130. In contrast, theclock signal CLL_A is generated only in a portion corresponding to thedetection channels 95 that correspond to the odd-numbered columns and isnot generated in a portion corresponding to the non-detection channels130 that correspond to the even-numbered columns. That is, thegeneration of the clock signal CLL_A pauses in the portion.

In the example in FIG. 46, the unit time T is the period required tooutput the digital signals DS(C) corresponding to two adjacent columns.As described above, since the generation of the clock signal CLL_Apauses in a portion corresponding to the even-numbered non-detectionchannel 130 of the two adjacent columns, the number of pulses per unittime T is ½ of that in the clock signal CLN_A.

FIG. 47 illustrates the second method for setting the number of pulsesper unit time in the clock signal of the ADC 77 to NPUL_A that is ½ ofNPUN_A in the image reading operation. Similarly to FIG. 46, (A) of FIG.47 illustrates a clock signal CLN_A in the image reading operation and(B) of FIG. 47 illustrates a clock signal CLL_A in the AED operation.The clock signal CLN_A in the image reading operation is exactly thesame as that in FIG. 46. In contrast, the pause period illustrated in(B) of FIG. 46 is not provided in the clock signal CLL_A in the AEDoperation and the period of the clock signal CLL_A is 2TC that is twiceas long as the period TC of the clock signal CLN_A.

In the example illustrated in FIG. 47, the unit time T is the period 2TCof the clock signal CLL_A. In the period 2TC, while the number of pulsesin the clock signal CLN_A is two, the number of pulses in the clocksignal CLL_A is one. Therefore, the number of pulses per unit time T inthe clock signal CLN_A is ½ of that in the clock signal CLN_A, similarlyto FIG. 46.

FIG. 48 is a flowchart illustrating the procedure of the operation ofthe electronic cassette according to the (3-1)-th embodiment. Theflowchart differs from the flowchart illustrated in FIG. 17 in the(1-1)-th embodiment in Steps ST1203 and ST1803 surrounded by a one-dotchain line. Hereinafter, only the difference will be described.

In Step ST1203, in the AED operation, the analog voltage signals V(C)from the detection CAs 132 are selectively output to the ADC 77 and theADC 77 performs only the AD conversion process for the selectivelyoutput analog voltage signal V(C). Then, the number of pulses per unittime T in the clock signal of the ADC 77 is reduced to be less than thatin the image reading operation (irradiation start detection step). InStep ST1803, in the image reading operation, the number of pulses perunit time T in the clock signal of the ADC 77 is set to the normalnumber of pulses (NPUN_A) (image reading step).

As such, since the number of pulses per unit time T in the clock signalof the ADC 77 in the AED operation is less than that in the imagereading operation, it is possible to reduce the consumption of powerrequired for driving the ADC 77 in the AED operation and thus to reducethe power consumption of the signal processing circuit 51 in the AEDoperation. Therefore, similarly to the first and second inventions, thebattery 65 lasts longer than that in the related art. As a result, thenumber of times the battery 65 is charged is reduced and thus it ispossible to improve imaging efficiency.

In FIG. 44, for convenience of explanation, half of the columns in onearea AR are set as the detection channels 95. However, as described inthe (1-8)-th embodiment, the detection channels 95 may be set by anymethod.

(3-2)-th Embodiment

FIG. 49 illustrates a (3-2)-th embodiment. In the (3-1)-th embodiment,the MUX 135 having a function of selecting the analog voltage signalsV(C) from some of a plurality of connected CAs 60 is used. However, in acase in which the MUX 135 having the above-mentioned function is notpresent as a general-purpose product, it takes a lot of time and effortto implement the function and it costs to implement the function. Forexample, the MUX 76 that has only the function of sequentially selectingthe columns one by one is modified into the MUX 135 or the MUX 135 withthe above functions is custom-made. Therefore, in the (3-2)-thembodiment illustrated in FIG. 49, the analog voltage signals V(C) fromsome CAs are selectively output to the ADC 77 while a general MUX 76 isused.

FIG. 49 illustrates a circuit configuration of the detection channel 95in the (3-2)-th embodiment. The detection channel 95 is divided into afirst path 140 that is connected to the MUX 76 and a second path 141that is connected to the ADC 77 without passing through the MUX 76 in astage behind the CDS 61. The first path 140 is a path that outputs theanalog voltage signal V(C) from the detection CA 132 to the ADC 77through the MUX 76. In contrast, the second path 141 is a path thatoutputs the analog voltage signal V(C) to the ADC 77 without passingthrough the MUX 76.

A switch 142 is connected to the detection channel 95, the first path140, and the second path 141. The control unit 54 controls the drivingof the switch 142 to switch the path connected to the detection channel95 between the first path 140 and the second path 141.

FIG. 49A illustrates a case in which the AED operation is performed andFIG. 49B illustrates a case in which the image reading operation isperformed. That is, the second path 141 is selected by the switch 142 inthe AED operation and the first path 140 is selected by the switch 142in the image reading operation.

As such, the detection channel 95 is divided into the first path 140that outputs the analog voltage signal V(C) from the detection CA 132 tothe ADC 77 through the MUX 76 and the second path 141 that outputs theanalog voltage signal V(C) from the detection CA 132 to the ADC 77without passing through the MUX 76. Therefore, in the AED operation, theswitch 142 is controlled such that the second path 141 is selected.Therefore, it is not necessary to prepare the special MUX 135 describedin the (3-1)-th embodiment illustrated in FIG. 44 and it is possible tosave time and costs.

As described above, each embodiment of the third invention may becombined with each embodiment of the first invention and the secondinvention. For example, as in the second invention, the first inventionmay be applied such that the control unit 54 periodically switches thepower supply state of the ADC 77 and the MUX 76 which form the block BLbetween the first state and the second state, as illustrated in FIG. 14in the (1-1)-th embodiment. The first state and the second state aredefined as described at the end of the second invention.

As in the second invention, the switching patterns of power supply tothe ADC 77 and the block BL in the third invention and the firstinvention may be combined as follows. First, in a case in which thereare two or more blocks BL including the MUX 76 and the ADC 77 whosepower supply state is periodically switched as illustrated in, forexample, FIG. 14 of the (1-1)-th embodiment, the control unit 54 mayshift the switching timing of the power supply state of at least two ofthe two or more blocks BL.

In addition, the control unit 54 may shift the switching timing of thepower supply state for each of a plurality of groups to which two ormore blocks BL belong, as illustrated in, for example, FIG. 14 of the(1-1)-th embodiment. In this case, it is preferable that at least oneblock BL is disposed between two blocks BL belonging to the same group.Alternatively, as illustrated in, for example, FIG. 18 of the (1-2)-thembodiment, the switching timing of the power supply state of all of thetwo or more blocks BL may be shifted.

For example, as illustrated in FIG. 21 of the (1-5)-th embodiment, in acase in which there are a plurality of blocks BL including the MUX 76 towhich some CAs are not connected, control may be performed such that atleast one of the blocks BL is always in the second state.

As in the (1-12)-th embodiment illustrated in FIGS. 35 to 37, leakcharge correction and temperature drift correction may be performed forthe dose signal DDS(C).

For example, in a case in which the (1-12)-th embodiment illustrated inFIGS. 35 to 37 is applied to the configuration of the (3-1)-thembodiment illustrated in FIG. 44, some CAs that selectively output theanalog voltage signal V(C) to the ADC 77 are the detection CA 132connected to the detection channel 95 illustrated in FIG. 44 and the CA60 connected to the reference channel 120 illustrated in FIG. 37. Thatis, in the (3-1)-th and (3-2)-th embodiments, only the detection CA 132has described as some CAs that selectively output the analog voltagesignal V(C) to the ADC 77. However, the invention is not limitedthereto. The CA 60 connected to the reference channel 120 is alsoincluded.

In addition, the (1-8)-th embodiment illustrated in FIGS. 25 to 27 inwhich the detection channel 95 that is the signal line 42 to which thedetection pixel 90 used for the AED operation is connected is set, the(1-9)-th embodiment illustrated in FIGS. 28 to 31 in which the detectionpixel 90X used only for the AED operation is provided, the (1-10)-thembodiment illustrated in FIG. 32 in which the setting of the detectionpixel 90 can be changed, the (1-11)-th embodiment illustrated in FIGS.33 and 34 in which the operation of the CDS 61 in the AED operation issimplified, and the (1-13)-th embodiment illustrated in FIG. 38 in whichthe digital signal transmission I/F is switched may be combined witheach other.

Further, the (2-1)-th to (2-3)-th embodiments of the second inventionillustrated in FIGS. 39 to 43 may be applied to change at least one ofthe non-selected CAs other than some CAs that selectively output theanalog voltage signal V(C) to the ADC 77 to the power saving state inwhich power supplied to the non-selected CAs in the AED operation islower than normal power in the image reading operation.

Here, the non-selected CA is the non-detection CA 131 in a case in whichthe (1-12)-th embodiment illustrated in FIGS. 35 to 37 is not appliedand is the non-detection CA 131 other than the CA 60 connected to thereference channel 120 in a case in which the (1-12)-th embodiment isapplied.

In a case in which the (2-3)-th embodiment is applied, not only thenon-detection CA 131 but also at least one of the detection CAs 132(including the CA 60 connected to the reference channel 120 in a case inwhich the (1-12)-th embodiment is applied) is driven in a low powerstate in which power lower than the normal power PN_C and is greaterthan 0 is supplied. Therefore, it is possible to further reduce thepower consumption of the signal processing circuit 51 in the AEDoperation.

4. Fourth Invention

An object of a fourth invention illustrated in FIGS. 50 to 58 which willbe described below is to solve the problems occurring in a case in whichthe AED operation is performed while the power supply state of aplurality of ADCs 77 and a plurality of blocks BL1 to BL16 according tothe first invention is switched. In the fourth invention, the controlunit 54 switches each of the plurality of blocks BL1 to BL16 from thesecond state to the first state a predetermined time, which is requiredto stably operate, for example, the ADC 77 forming the block BL, beforethe start timing of charge reading in the AED operation.

In the fourth invention, similarly to the second and third inventions,for example, the X-ray imaging system 10 and the electronic cassette 16have the same basic configuration as those in the first invention. Inaddition, the patterns described in the (1-1)-th to (1-7)-th embodimentscan be applied to the switching pattern of the power supply state of theADC 77. Further, the fourth invention may be combined with otherembodiments (the (1-8)-th to (1-13)-th embodiments) of the firstinvention, the (2-1)-th to (2-3)-th embodiments of the second invention,and the (3-1)-th and (3-2)-th embodiments of the third invention.Hereinafter, the same components as those in the first to thirdinventions are denoted by the same reference numerals and thedescription thereof will not be repeated. The difference from the firstto third inventions will be mainly described.

(4-1)-th Embodiment

FIGS. 50 and 51 illustrate a (4-1)-th embodiment. In the (4-1)-thembodiment, similarly to the (2-1)-th and (3-1)-th embodiments, forexample, a configuration including the detection pixel 90X1 illustratedin FIG. 29 or the detection pixel 90X2 illustrated in FIG. 30 in the(1-9)-th embodiment will be described. However, the configuration is notlimited thereto.

FIG. 50 illustrates the power supply state of a certain block BL. Ahatched portion is the period for which charge that is the source of thedose signal DDS(C) is read. Specifically, for the period, a series ofoperations in which the CA 60 reads charge through the signal line 42,the MUX 76 sequentially selects the CA 60 and outputs the analog voltagesignal V(C) based on the charge to the ADC 77, and the ADC 77 convertsthe analog voltage signal V(C) into the dose signal DDS(C) and outputsthe dose signal DDS(C) is performed.

Here, the operation of the block BL becomes unstable due to, forexample, the influence of temperature drift immediately after the blockBL is switched from the non-operating state which is the second state tothe operating state which is the first state. The reliability of thedose signal DDS(C) output while the operation is unstable issignificantly reduced. Therefore, there is a concern that thereliability of the determination of whether the emission of X-rays hasbeen started will not be maintained.

FIG. 50A illustrates an example in which the reading of charge startsimmediately after the block BL is switched from the non-operating stateto the operating state. As such, in a case in which there is not enoughtime between the switching of the block BL from the non-operating stateto the operating state and the timing when the reading of charge starts,the risk that the start of the emission of X-rays will be erroneouslydetermined increases according to the dose signal DDS(C) output whilethe operation of the block BL is unstable.

Therefore, as illustrated in FIG. 50B, the block BL is switched from thenon-operating state to the operating state a time TW before the timingwhen the reading of charge starts. The time TW is the time required tostably operate the block BL.

FIG. 51 is a flowchart illustrating the procedure of the operation ofthe electronic cassette according to the (4-1)-th embodiment. Theflowchart differs from the flowchart illustrated in FIG. 17 of the(1-1)-th embodiment in Steps ST1204 and ST1804 surrounded by a one-dotchain line. Hereinafter, only the difference will be described.

In Step ST1204, in the AED operation, the control unit 54 switches thepower supply state of the block BL. Then, the block BL is switched fromthe non-operating state to the operating state the time TW before thetiming when the reading of charge starts (irradiation start detectionstep). Further, in Step ST1804, in the image reading operation, all ofthe blocks BL are switched to the operating state (image reading step).

Then, as illustrated in FIG. 50A, the dose signal DDS(C) is not outputwhile the operation of the block BL is unstable and it is possible toreduce the concern that the start of the emission of X-rays will beerroneously determined.

There are three variations illustrated in FIGS. 52 to 54 in the periodfor which charge is read. The period is hatched in FIGS. 52 to 54. FIGS.52 to 54 illustrate the block BL1 that is in charge of the area AR1corresponding to the first to 144th columns, similarly to FIGS. 9 and44.

First, FIG. 52 illustrates a case in which all of the signal lines 42 inthe area AR1 that the blocks BL1 is in charge of are the detectionchannels 95, as represented by alphabets DT (see FIG. 44). In this case,the period for which charge is read is the period for which the dosesignals DDS(1) to DDS(144) based on the analog voltage signals V(1) toV(144) from the detection CAs 132 of the detection channels 95 areoutput.

FIG. 53 illustrates a case in which the odd-numbered columns are thedetection channels 95 and the MUX is not the MUX 135 having a functionof selecting the analog voltage signals V(C) from the detection CAs 132of the detection channels 95, but is the general MUX 76 having only thefunction of sequentially selecting the columns one by one, similarly tothe (3-1)-th embodiment illustrated in FIG. 44. In this case, the periodfor which charge is read is the period for which the dose signalsDDS(1), DDS(3), DDS(5), . . . , DDS(144) based on the analog voltagesignals V(1), V(3), V(5), . . . , V(143) from the detection CAs 132 ofthe detection channels 95 corresponding to the odd-numbered columns areoutput. That is, in this case, the period for which charge is read isintermittent.

FIG. 54 illustrates a case in which the odd-numbered columns are thedetection channels 95 as in FIG. 52 and the MUX is not the MUX 76, butis the MUX 135. In this case, the period for which charge is read is thesum of the periods for which the dose signals DDS(1), DDS(3), DDS(5), .. . , DDS(144) based on the analog voltage signals V(1), V(3), V(5), . .. , V(143) from the detection CAs 132 of the detection channels 95corresponding to the odd-numbered columns are output. Since the periodfor which charge is read is not intermittent unlike FIG. 53, the simpleappearance is the same as that in FIG. 52. However, while the MUX 76sequentially selects the analog voltage signals V(C) corresponding tothe columns one by one in FIG. 52, the MUX 135 selects the analogvoltage signal V(C) for every other column in FIG. 54.

(4-2)-th Embodiment

FIGS. 55 to 57 illustrate a (4-2)-th embodiment. In the (4-1)-thembodiment, the timing when the block BL is switched from thenon-operating state to the operating state with respect to the timingwhen the reading of charge starts is defined. However, in the (4-2)-thembodiment, the timing when the block BL is switched from the operatingstate to the non-operating state is defined.

In a case in which a certain block BL is switched from the operatingstate to the non-operating state and charge is being read in anotherblock BL, there is a concern that, for example, switching noisegenerated by the switching of the block BL from the operating state tothe non-operating state will be mixed with charge in another block BL.Therefore, in the (4-2)-th embodiment, a certain block BL is switchedfrom the operating state to the non-operating state at a timing thatdoes not overlap the timing when charge is read in another block BL.

FIGS. 55 to 57 illustrate a case in which the power supply state of eachof the blocks BL1 to BL16 (the block BL5 and the subsequent blocks arenot illustrated) is periodically switched and the timing when the powersupply state of each of the blocks BL1 to BL16 is switched is shifted,similarly to FIG. 14 of the (1-1)-th embodiment or FIG. 18 of the(1-2)-th embodiment. FIGS. 55 and 56 illustrate a case in which theperiod for which charge is read is a variation of FIG. 52 or FIG. 54 andFIG. 57 illustrates a case in which the period for which charge is readis a variation of FIG. 53.

FIG. 55 illustrates an example in which each of the blocks BL1 to BL16is switched from the operating state to the non-operating state at thetiming before reading of charge from the detection CAs 132 in each ofthe blocks BL1 to BL16 starts, specifically, for the time TW, asrepresented by a dashed arrow. Specifically, in FIG. 55, the controlunit 54 switches the block BL1 from the operating state to thenon-operating state while the block BL2 is operating and switches theblock BL2 from the operating state to the non-operating state while theblock BL3 is operating. In addition, the control unit 54 switches theblock BL3 from the operating state to the non-operating state while theblock BL4 is operating.

FIG. 56 illustrates an example in which each of the blocks BL1 to BL16is switched from the operating state to the non-operating state at thetiming after the reading of charge from the detection CAs 132 in each ofthe blocks BL1 to BL16 ends. Specifically, in FIG. 56, the control unit54 switches the block BL1 from the operating state to the non-operatingstate after the reading of charge in the block BL2 ends and switches theblock BL2 from the operating state to the non-operating state after thereading of charge in the block BL3 ends. In addition, the control unit54 switches the block BL3 from the operating state to the non-operatingstate after the reading of charge in the block BL4 ends.

FIG. 57 illustrates an example in which each of the blocks BL1 to BL16is switched from the operating state to the non-operating state betweenthe intermittent periods for which charge is read in the blocks BL1 toBL16. Specifically, in FIG. 57, the control unit 54 switches the blockBL1 from the operating state to the non-operating state between theintermittent periods for which charge is read in the block BL2 andswitches the block BL2 from the operating state to the non-operatingstate between the intermittent periods for which charge is read in theblock BL3. Then, the control unit 54 switches the block BL3 from theoperating state to the non-operating state between the intermittentperiods for which charge is read in the block BL4.

As such, in a case in which the block BL is switched from the operatingstate to the non-operating state at a timing that does not overlap thetiming when charge is read in another block BL, there is no concernthat, for example, switching noise generated by the switching of theblock BL from the operating state to the non-operating state will bemixed with charge in another block BL.

Among the examples illustrated in FIGS. 55 to 57, the exampleillustrated in FIG. 55 in which each of the blocks BL1 to BL16 isswitched from the operating state to the non-operating state before thereading of charge in each of the blocks BL1 to BL16 starts is mostpreferable in terms of power saving.

(4-3)-th Embodiment

FIG. 58 illustrates a (4-3)-th embodiment. As illustrated in FIG. 35 ofthe (1-12)-th embodiment, in a case in which the power supply state ofeach block BL is switched in the AED operation, the temperaturedistribution in the block BL is biased. In a case in which the bias ofthe temperature distribution is not removed until the image readingoperation for obtaining the X-ray image provided for diagnosis, atemperature drift occurs in the image signal DIS(C) and the quality ofthe X-ray image is degraded. Therefore, in the (4-3)-th embodiment, thecontrol unit 54 switches all of the blocks BL to the operating stateuntil the image reading operation starts after the start of the emissionof X-rays is detected in the AED operation.

In FIG. 58, all of the blocks BL1 to BL16 are switched to the operatingstate at the timing when the start of the emission of X-rays is detectedin the AED operation. Specifically, in FIG. 58, the control unit 54switches the blocks BL (blocks BL3, BL4, BL7, BL8, BL11, BL12, BL15, andBL16) in the non-operating state in a case in which the start of theemission of X-rays is detected to the operating state. In contrast, thecontrol unit 54 maintains the blocks BL (for example, the blocks BL1 andBL2 other than the above) in the operating state in a case in which thestart of the emission of X-rays is detected in the operating state.

In FIG. 58, since all of the blocks BL1 to BL16 are switched to theoperating state at the timing when the start of the emission of X-raysis detected in the AED operation, all of the blocks BL1 to BL16 areswitched to the operating state for a reading period TX of the dosesignal DDS(C) where one cycle of the switching of all of the blocks BL1to BL16 ends after the start of the emission of X-rays is detected.

As such, since all of the blocks BL are switched to the operating stateuntil the image reading operation starts after the start of the emissionof X-rays is detected in the AED operation, it is highly possible thatthe bias of the temperature distribution in the block BL caused by theswitching of the power supply state of each block BL in the AEDoperation has been removed in the image reading operation. Therefore, atemperature drift does not occur in the image signal DIS(C) due to thebias of the temperature distribution in the block BL and it is possibleto obtain a high-quality X-ray image.

In addition, since all of the blocks BL1 to BL16 are switched to theoperating state for the reading period TX of the dose signal DDS(C)where one cycle of the switching of all of the blocks BL1 to BL16 endsafter the start of the emission of X-rays is detected, it is possible tosecure the time sufficient to remove the bias of the temperaturedistribution in the block BL until the image reading operation starts.

Further, all of the blocks BL1 to BL16 may be switched to the operatingstate at any timing of the period from the detection of the start of theemission of X-rays in the AED operation to the start of the imagereading operation. However, it is preferable that all of the blocks BL1to BL16 are switched to the operating state at the timing when the startof the emission of X-rays is detected in the AED operation asillustrated in FIG. 58, in order to reliably remove the bias of thetemperature distribution in the block BL. The operating state, thenon-operating state, the first state, and the second state are definedas described at the end of the second invention.

The time TW required to stably operate the block BL may be substantiallyequal to or longer than the time required to prepare for the operationof the CA 60, the CDS 61, the MUX 76, and the ADC 77 forming the blockBL. The fourth invention also includes the case in which the time TWrequired to stably operate the block BL is substantially equal to thetime required to prepare for the operation of the CA 60, the CDS 61, theMUX 76, and the ADC 77 forming the block BL. That is, the fourthinvention also includes a case in which the reading of charge startsimmediately after the CA 60, the CDS 61, the MUX 76, and the ADC 77forming the block BL are ready for operation.

In addition, power supplied to each component of the block BL for thetime TW may be changed depending on the temperature of the block BL. Forexample, in a case in which the temperature of the block BL before thetime TW is significantly lower than a target temperature, the controlunit 54 supplies relatively high power to each component of the block BLsuch that the temperature reaches the target temperature in a shorttime. In contrast, in a case in which the temperature of the block BLbefore the time TW is lower than the target temperature, but isrelatively close to the target temperature and relatively high power issupplied to each component of the block BL, there is a concern that thetemperature will exceed the target temperature. Therefore, the controlunit 54 operates each component of the block BL with relatively lowpower.

As described above, each embodiment of the fourth invention may becombined with each embodiment of the first invention, the secondinvention, and the third invention. For example, as in the second andthird inventions, the first invention may be applied such that thecontrol unit 54 periodically switches the power supply state of the ADC77 and the MUX 76 which form the block BL between the first state andthe second state, as illustrated in FIG. 14 in the (1-1)-th embodiment.

As in the second and third inventions, the switching patterns of powersupply to the ADC 77 and the block BL in the fourth invention and thefirst invention may be combined as follows. First, in a case in whichthere are two or more blocks BL including the MUX 76 and the ADC 77whose power supply state is periodically switched as illustrated in, forexample, FIG. 14 of the (1-1)-th embodiment, the control unit 54 mayshift the switching timing of the power supply state of at least two ofthe two or more blocks BL.

In addition, the control unit 54 may shift the switching timing of thepower supply state for each of a plurality of groups to which two ormore blocks BL belong, as illustrated in, for example, FIG. 14 of the(1-1)-th embodiment. In this case, it is preferable that at least oneblock BL is disposed between two blocks BL belonging to the same group.Alternatively, as illustrated in, for example, FIG. 18 of the (1-2)-thembodiment, the switching timing of the power supply state of all of thetwo or more blocks BL may be shifted.

As illustrated in, for example, FIG. 21 of the (1-5)-th embodiment, in acase in which there are a plurality of blocks BL including the MUX 76 towhich only the non-detection CA 131 is connected, at least one of theplurality of blocks BL may be always in the second state.

As in the (1-12)-th embodiment illustrated in FIGS. 35 to 37, leakcharge correction and temperature drift correction may be performed forthe dose signal DDS(C).

In addition, the (1-8)-th embodiment illustrated in FIGS. 25 to 27 inwhich the detection channel 95 that is the signal line 42 to which thedetection pixel 90 used for the AED operation is connected is set, the(1-9)-th embodiment illustrated in FIGS. 28 to 31 in which the detectionpixel 90X used only for the AED operation is provided, the (1-10)-thembodiment illustrated in FIG. 32 in which the setting of the detectionpixel 90 can be changed, the (1-11)-th embodiment illustrated in FIGS.33 and 34 in which the operation of the CDS 61 in the AED operation issimplified, and the (1-13)-th embodiment illustrated in FIG. 38 in whichthe digital signal transmission I/F is switched may be combined witheach other.

Further, the (2-1)-th to (2-3)-th embodiments of the second inventionillustrated in FIGS. 39 to 43 may be applied to change at least one ofthe non-selected CAs other than some CAs that selectively output theanalog voltage signal V(C) to the ADC 77 to the power saving state inwhich power supplied to the non-selected CAs in the AED operation islower than normal power in the image reading operation.

In addition, the (3-1)-th and (3-2)-th embodiments illustrated in FIGS.44 to 49 in which the number of pulses per unit time in the clock signalof the ADC 77 is less than that in the image reading operation may beapplied.

5. Fifth Invention

In a fifth invention illustrated in FIGS. 59 and 60 which will bedescribed below, the control unit 54 reduces the power supplied to theCA 60 in the AED operation to be lower than that in the image readingoperation. In the second invention, at least one of the non-detectionCAs 131 is changed to the power saving state in which power supplied tothe non-detection CA in the AED operation is lower than the normal powerin the image reading operation. However, the fifth invention differsfrom the second invention in that power supplied to the CAs 60 in theAED operation is lower than that in the image reading operation, withoutdistinguishing between the detection CA 132 and the non-detection CA131.

In the fifth invention, similarly to the second to fourth inventions,for example, the X-ray imaging system 10 and the electronic cassette 16have the same basic configuration as those in the first invention.Hereinafter, the same components as those in the first to fourthinventions are denoted by the same reference numerals and thedescription thereof will not be repeated. The difference from the firstto fourth inventions will be mainly described.

As illustrated in FIG. 59, the control unit 54 sets the power P_Csupplied to all of the CAs 60 in the image reading operation to normalpower PN_C and sets the power P_C supplied to all of the CAs 60 in theAED operation to PL_C that is lower than PN_C.

FIG. 60 is a flowchart illustrating the procedure of the operation ofthe electronic cassette according to the fifth invention. The flowchartdiffers from the flowchart illustrated in FIG. 17 of the (1-1)-thembodiment in Steps ST1205 and ST1805 surrounded by a one-dot chainline. Hereinafter, only the difference will be described.

In Step ST1205, in the AED operation, all of the CAs 60 are driven withthe low supply power PL_C. In contrast, in the image reading operationof Step ST1805, all of the CAs 60 are driven with the normal power PN_C.

As such, since the power supplied to the CA 60 in the AED operation islower than that in the image reading operation, it is possible to reducethe power consumption of the signal processing circuit 51 in the AEDoperation. Therefore, as in the first to third inventions, the battery65 lasts longer than that in the related art. As a result, the number oftimes the battery 65 is charged is reduced and thus it is possible toimprove imaging efficiency.

It is possible to understand a radiographic image detection devicedescribed in the following Supplementary Note 1 and a method foroperating a radiographic image detection device described in thefollowing Supplementary Note 2 from the above description.

[Supplementary Note 1]

There is provided a radiographic image detection device comprising: asensor panel in which pixels that are sensitive to radiation which hasbeen emitted from a radiation generation apparatus and transmittedthrough a subject and accumulate charge are two-dimensionally arrangedand a plurality of signal lines for reading the charge are arranged; asignal processing circuit that reads an analog voltage signalcorresponding to the charge from the pixel through the signal line toperform signal processing; a plurality of charge amplifiers which areincluded in the signal processing circuit and each of which is providedfor each signal line, is connected to one end of the signal line, andconverts the charge from the pixel into the analog voltage signal; amultiplexer that is included in the signal processing circuit, has aplurality of input terminals to which the plurality of charge amplifiersare connected, sequentially selects the analog voltage signals from theplurality of charge amplifiers, and outputs the selected analog voltagesignal; an AD converter that is included in the signal processingcircuit, is connected to a stage behind the multiplexer, and perform anAD conversion process of converting the analog voltage signal outputfrom the multiplexer into a digital signal corresponding to a voltagevalue; and a control unit that controls the signal processing circuitsuch that an irradiation start detection operation and an image readingoperation are performed. The irradiation start detection operation readsthe charge from the pixel through the signal line from before start ofthe emission of the radiation and detects the start of the emission ofthe radiation on the basis of the digital signal corresponding to theread charge. The image reading operation reads the charge from the pixelthrough the signal line after a pixel charge accumulation period forwhich the charge is accumulated in the pixel elapses from the start ofthe emission of the radiation and outputs a radiographic image which isindicated by the digital signal corresponding to the read charge and isprovided for diagnosis. The control unit reduces power supplied to allof the charge amplifiers in the irradiation start detection operation tobe lower than that in the image reading operation.

[Supplementary Note 2]

There is provided a method for operating a radiographic image detectiondevice comprising a sensor panel in which pixels that are sensitive toradiation which has been emitted from a radiation generation apparatusand transmitted through a subject and accumulate charge aretwo-dimensionally arranged and a plurality of signal lines for readingthe charge are arranged, a signal processing circuit that reads ananalog voltage signal corresponding to the charge from the pixel throughthe signal line to perform signal processing, a plurality of chargeamplifiers which are included in the signal processing circuit and eachof which is provided for each signal line, is connected to one end ofthe signal line, and converts the charge from the pixel into the analogvoltage signal, a multiplexer that is included in the signal processingcircuit, has a plurality of input terminals to which the plurality ofcharge amplifiers are connected, sequentially selects the analog voltagesignals from the plurality of charge amplifiers, and outputs theselected analog voltage signal, an AD converter that is included in thesignal processing circuit, is connected to a stage behind themultiplexer, and perform an AD conversion process of converting theanalog voltage signal output from the multiplexer into a digital signalcorresponding to a voltage value, and a control unit that controls thesignal processing circuit. The method comprises: an irradiation startdetection step of performing an irradiation start detection operationthat reads the charge from the pixel through the signal line from beforestart of the emission of the radiation and detects the start of theemission of the radiation on the basis of the digital signalcorresponding to the read charge; and an image reading step ofperforming an image reading operation that reads the charge from thepixel through the signal line after a pixel charge accumulation periodfor which the charge is accumulated in the pixel elapses from the startof the emission of the radiation and outputs a radiographic image whichis indicated by the digital signal corresponding to the read charge andis provided for diagnosis. Power supplied to all of the chargeamplifiers in the irradiation start detection step is lower than that inthe image reading operation.

The irradiation start detection step and the image reading stepdescribed in Supplementary Note 2 correspond to Step ST1205 and StepST1805 illustrated in FIG. 60, respectively.

6. Sixth Invention

In a sixth invention illustrated in FIGS. 61 and 62 which will bedescribed below, the control unit 54 reduces the number of pulses perunit time in the clock signal of the ADC 77 in the AED operation to beless than that in the image reading operation. In the third invention,the number of pulses per unit time in the clock signal of the ADC 77 inthe AED operation is reduced to be less than that in the image readingoperation by selectively outputting the analog voltage signals V(C) fromsome CAs including the detection CA 132 to the ADC 77 and causing theADC 77 to perform only the AD conversion process for the selectivelyoutput analog voltage signals V(C). In contrast, the sixth inventiondiffers from the third invention in that the number of pulses per unittime in the clock signal of the ADC 77 in the AED operation is reducedto be less than that in the image reading operation by causing the ADC77 to perform the AD conversion process for the analog voltage signalsV(C) from all of the CAs 60, without distinguishing between thedetection CA 132 and the non-detection CA 131, as in the image readingoperation.

In the sixth invention, similarly to the second to fifth inventions, forexample, the X-ray imaging system 10 and the electronic cassette 16 havethe same basic configuration as those in the first invention.Hereinafter, the same components as those in the first to fifthinventions are denoted by the same reference numerals and thedescription thereof will not be repeated. The difference from the firstto fourth inventions will be mainly described.

As illustrated in FIG. 61, the control unit 54 sets the number of pulsesNPU_A per unit time in the clock signals of all of the ADCs 77 to NPUN_Awhich is the normal number of pulses in the image reading operation andsets the number of pulses NPU_A to NPUL_A that is ½ of NPUN_A in the AEDoperation.

FIG. 62 is a flowchart illustrating the procedure of the operation ofthe electronic cassette according to the sixth invention. The flowchartdiffers from the flowchart illustrated in FIG. 17 of the (1-1)-thembodiment in Steps ST1206 and ST1806 surrounded by a one-dot chainline. Hereinafter, only the difference will be described.

In Step ST1206, in the AED operation, the clock signal in which thenumber of pulses NPUL_A is ½ of the normal number of pulses NPUN_A isapplied to all of the ADCs 77. In contrast, in the image readingoperation of Step ST1806, the normal clock signal with the number ofpulses NPUN_A is applied to all of the ADCs 77.

As such, since the number of pulses per unit time in the clock signal ofthe ADC 77 in the AED operation is less than that in the image readingoperation, it is possible to reduce the power consumption of the signalprocessing circuit 51 in the AED operation. Therefore, as in the firstto third inventions and the fifth invention, the battery 65 lasts longerthan that in the related art. As a result, the number of times thebattery 65 is charged is reduced and thus it is possible to improveimaging efficiency.

It is possible to understand a radiographic image detection devicedescribed in the following Supplementary Note 3 and a method foroperating a radiographic image detection device described in thefollowing Supplementary Note 4 from the above description.

[Supplementary Note 3]

There is provided a radiographic image detection device comprising: asensor panel in which pixels that are sensitive to radiation which hasbeen emitted from a radiation generation apparatus and transmittedthrough a subject and accumulate charge are two-dimensionally arrangedand a plurality of signal lines for reading the charge are arranged; asignal processing circuit that reads an analog voltage signalcorresponding to the charge from the pixel through the signal line toperform signal processing; a plurality of AD converters that areincluded in the signal processing circuit, perform an AD conversionprocess of converting the analog voltage signal into a digital signalcorresponding to a voltage value, and share the AD conversion processperformed for each of the signal lines; and a control unit that controlsthe signal processing circuit such that an irradiation start detectionoperation and an image reading operation are performed. The irradiationstart detection operation reads the charge from the pixel through thesignal line from before start of the emission of the radiation anddetects the start of the emission of the radiation on the basis of thedigital signal corresponding to the read charge. The image readingoperation reads the charge from the pixel through the signal line aftera pixel charge accumulation period for which the charge is accumulatedin the pixel elapses from the start of the emission of the radiation andoutputs a radiographic image which is indicated by the digital signalcorresponding to the read charge and is provided for diagnosis. In theirradiation start detection operation, for all of the AD converters, thecontrol unit reduces the number of pulses per unit time in a clocksignal which defines the operation timing of the AD converter to be lessthan that in the image reading operation.

[Supplementary Note 4]

There is provided a method for operating a radiographic image detectiondevice comprising a sensor panel in which pixels that are sensitive toradiation which has been emitted from a radiation generation apparatusand transmitted through a subject and accumulate charge aretwo-dimensionally arranged and a plurality of signal lines for readingthe charge are arranged, a signal processing circuit that reads ananalog voltage signal corresponding to the charge from the pixel throughthe signal line to perform signal processing, a plurality of ADconverters that are included in the signal processing circuit, performan AD conversion process of converting the analog voltage signal into adigital signal corresponding to a voltage value, and share the ADconversion process performed for each of the signal lines, and a controlunit that controls the signal processing circuit. The method comprises:an irradiation start detection step of performing an irradiation startdetection operation that reads the charge from the pixel through thesignal line from before start of the emission of the radiation anddetects the start of the emission of the radiation on the basis of thedigital signal corresponding to the read charge; and an image readingstep of performing an image reading operation that reads the charge fromthe pixel through the signal line after a pixel charge accumulationperiod for which the charge is accumulated in the pixel elapses from thestart of the emission of the radiation and outputs a radiographic imagewhich is indicated by the digital signal corresponding to the readcharge and is provided for diagnosis. In the irradiation start detectionstep, for all of the AD converters, the number of pulses per unit timein a clock signal which defines the operation timing of the AD converteris less than that in the image reading operation.

The irradiation start detection step and the image reading stepdescribed in Supplementary Note 4 correspond to Step ST1206 and StepST1806 illustrated in FIG. 62, respectively.

7. Seventh Invention

A seventh invention illustrated in FIGS. 63 and 64 which will bedescribed below is a modification example of the circuit configuration.In the seventh invention, similarly to the second to sixth inventions,for example, the X-ray imaging system 10 and the electronic cassette 16have the same basic configuration as those in the first invention.Hereinafter, the same components as those in the first to sixthinventions are denoted by the same reference numerals and thedescription thereof will not be repeated. The difference from the firstto fourth inventions will be mainly described.

FIGS. 63 and 64 illustrate the circuit configuration of one block BL andthe periphery thereof in the seventh invention. In the block BL, thedetection channel 95 and the non-detection channel 130 are mixed as inthe (2-1)-th embodiment illustrated in FIG. 39. As in the (3-2)-thembodiment illustrated in FIG. 49, the detection channel 95 is dividedinto the first path 140 and the second path 141 in a stage behind theCDS 61 and the switch 142 is connected to the detection channel 95. Theswitch 142 switches the path connected to the detection channel 95 tothe first path 140 or the second path 141 in response to a drivingcontrol signal S_MUX input from the control unit 54.

Each of the detection channel 95 and the non-detection channel 130 isdivided into a first path 200 and a second path 201 in a stage beforethe detection CA 132 and the non-detection CA 131. The first paths 200are connected to the detection CA 132 and the non-detection CA 131. Thesecond paths 201 are connected to the CDSs 61 without passing throughthe detection CA 132 and the non-detection CA 131, respectively. Thefirst paths 200 are for inputting charge to the detection CA 132 and thenon-detection CA 131. The second paths 201 are for outputting charge tothe MUX 76 without passing through the detection CA 132 and thenon-detection CA 131.

A switch 202 is connected to the detection channel 95 or thenon-detection channel 130, the first path 200, and the second path 201.The switch 202 switches the path connected to the detection channel 95or the non-detection channel 130 to the first path 200 or the secondpath 201 in response to a driving control signal S_CA input from thecontrol unit 54.

Similarly, each of the detection channel 95 and the non-detectionchannel 130 is divided into a first path 203 and a second path 204 inthe stage before the CDS 61 and a switch 205 is connected to each of thedetection channel 95 and the non-detection channel 130. The switch 205switches the path connected to the detection channel 95 or thenon-detection channel 130 to the first path 203 or the second path 204in response to a driving control signal S_CDS input from the controlunit 54.

A bias power supply 207 is connected to the detection channel 95 and thenon-detection channel 130 through switches 206. The switch 206 is turnedon and off in response to a driving control signal S_BIAS input from thecontrol unit 54.

The control unit 54 outputs the driving control signals S_MUX, S_CA, andS_CDS to the switches 142, 202, and 205 of the channels 95 and 130 (eachsignal line 42), respectively. Therefore, the control unit 54 canindividually control the driving of each of the switches 142, 202, 205.For example, the control unit 54 controls the switches 202 and 205 ofthe detection channel 95 such that they are connected to the first paths200 and 203 and controls the switches 202 and 205 of the non-detectionchannel 130 such that they are connected to the second paths 201 and204. Similarly, for example, the control unit 54 can individually outputthe driving control signal S_BIAS to the switches 206 such that thedetection channel 95 is turned off and the non-detection channel 130 isturned on.

FIG. 63 illustrates a case in which the image reading operation isperformed. That is, the first paths 140, 200, and 203 in each of thechannels 95 and 130 are selected by the switches 142, 202, and 205,respectively. In addition, each switch 206 is in an off state.

In contrast, in the AED operation, for example, the state illustrated inFIG. 64 is obtained. That is, in the detection channel 95, the secondpath 141 is selected by the switch 142 and the first paths 200 and 203are selected by the switches 202 and 205, respectively. The switch 206is still in the off state. This state is the same as that illustrated inFIG. 49A of the (3-2)-th embodiment. Therefore, as described in the(3-2)-th embodiment, the analog voltage signal V(C) from the detectionCA 132 is directly output to the ADC 77 without passing through the MUX76.

In contrast, in the non-detection channel 130, the second paths 201 and204 are selected by the switches 202 and 205, respectively. In addition,the switch 206 is in an on state. In this case, the charge of thenon-detection channel 130 is directly output to the MUX 76 withoutpassing through the non-detection CA 131 and the CDS 61. A bias voltageis applied from the bias power supply 207 to the non-detection channel130 through the switch 206.

In this case, the non-detection CA 131 is in a power-off state in whichthe supply power PL_C is 0, as in the (2-2)-th embodiment illustrated inFIG. 41. The CDS 61 of the non-detection channel 130 is also in thepower-off state.

In a case in which the non-detection CA 131 is in the power-off state,as described in the (2-2)-th embodiment, the virtual short state betweentwo input terminals of the non-detection CA 131 is not maintained andthe potential of the input stage of the non-detection CA 131 becomesindefinite. Then, the charge of the non-detection channel 130 alsobecomes unstable, which has a bad influence on the image readingoperation later. Therefore, in the seventh invention, the switch 206 isturned on to apply the bias voltage from the bias power supply 207 tothe non-detection channel 130. Then, it is possible to solve the problemthat the charge of the non-detection channel 130 becomes unstable, whichhas a bad influence on the image reading operation later.

In addition, the non-detection CA 131 may not be in the power-off state,but the supply power PL_C that does not cause the potential of the inputstage to be indefinite may be supplied to change the non-detection CA131 to the low power state as in the (2-1)-th embodiment.

As in the (2-3)-th embodiment illustrated in FIG. 43, in addition to thenon-detection CA 131, the detection CA 132 may be driven in the lowpower state in which power lower than the normal power PN_C and isgreater than 0 is supplied. However, in this case, as illustrated inFIG. 64, in the AED operation, in the detection channel 95, the secondpath 141 is selected by the switch 142, the first paths 200 and 203 areselected by the switches 202 and 205, respectively, and the switch 206is turned off.

In a case in which the detection CA 132 is driven in the low powerstate, the detection performance of the detection CA 132 is degraded. Asa result, there is a concern that the S/N ratio of the dose signalDDS(C) will be reduced. For this reason, it is preferable that thenumber of gate lines 41 to which the gate pulses G(R) are applied at thesame time by the gate driving unit 50 is increased to increase theamount of charge added in the detection channel 95, thereby improvingthe S/N ratio of the dose signal DDS(C).

The control unit 54 may not output the driving control signals S_MUX,S_CA, S_CDS, and S_BIAS to the switches 142, 202, 205, and 206 of thechannels 95 and 130 (each signal line 42), respectively, but mayuniformly output the driving control signals S_MUX, S_CA, S_CDS, S_BIASin units of the blocks BL. For example, as in the (1-5)-th embodiment,in the blocks BL in which the ADC 77 is always in the non-operatingstate, the switches 142, 202, and 205 are uniformly connected to thesecond paths 141, 201, and 204, respectively, and the switch 206 isuniformly turned on.

The switch 206 and the bias power supply 207 may be provided in theblock BL or the signal processing circuit 51.

The detection CA 132 is switched to the power-off state and the switch206 is turned on to apply the bias voltage from the bias power supply207 to the detection channel 95 such that the switches 202 and 205 ofthe detection channel 95 are connected to the second paths 201 and 204,respectively. Then, the ADC 77 converts a variation in the load of thebias power supply 207 caused by a current flowing to the pixel 40 in acase in which X-rays are emitted into the digital signal DS(C). Thedigital signal DS(C) is used as the dose signal DDS(C). In a case inwhich a variation in the dose signal DS(C) is out of a predeterminedrange, it may be determined that the emission of X-rays has started.

Similarly, the non-detection CA 131 is switched to the power-off stateand the switch 206 is turned on to apply the bias voltage from the biaspower supply 207 to the non-detection channel 130 such that the switches202 and 205 of the non-detection channel 130 are connected to the secondpaths 201 and 204, respectively. Then, the ADC 77 converts a variationin the load of the bias power supply 207 caused by a current flowing tothe pixel 40 in a case in which X-rays are emitted into the digitalsignal DS(C). The digital signal DS(C) is used as the dose signalDDS(C). In a case in which a variation in the dose signal DS(C) is outof a predetermined range, it may be determined that the emission ofX-rays has started.

Alternatively, it may be determined whether the emission of X-rays hasstarted on the basis of both the dose signal DDS(C) which has beenoutput from the detection channel 95 and indicates a variation in theload of the bias power supply 207 and the dose signal DDS(C) which hasbeen output from the non-detection channel 130 and indicates a variationin the load of the bias power supply 207. Specifically, the differenceor ratio between the dose signals DDS(C) may be calculated and it may bedetermined whether the emission of X-rays has started on the basis ofthe calculated difference or ratio. In this case, since an impact or anoise component, such as vibration noise and electromagnetic noise,applied to the electronic cassette 16 is canceled, it is possible toreduce a concern that the start of the emission of X-rays will beerroneously determined due to the noise component.

The detection CA 132 or the non-detection CA 131 may not be changed tothe power-off state, but the power PL_C that does not cause thepotential of the input stage of the detection CA 132 or thenon-detection CA 131 to be indefinite may be supplied to change thedetection CA 132 or the non-detection CA 131 to the low power state asin the (2-1)-th embodiment.

The power supply for acquiring the dose signal DDS(C) indicating a loadvariation is not limited to the bias power supply 207. Any power supply,such as a power supply for the ADC 77, the CA 60, or the CDS 61, may beused as long as it is turned on during the AED operation.

However, in a case in which whether the emission of X-rays has startedis determined on the basis of the dose signal DDS(C) indicating avariation in the load of the power supply, the variation in the load ofthe power supply is small. Therefore, the S/N ratio of the dose signalDDS(C) is reduced and there is a concern that the X-ray emission startdetection performance will be degraded.

For this reason, it is preferable that the number of gate lines 41 towhich the gate pulses G(R) are applied at the same time by the gatedriving unit 50 is increased to increase the amount of charge added inthe detection channel 95 or the non-detection channel 130, therebyimproving the S/N ratio of the dose signal DDS(C). Alternatively, thedose signals DDS(C) between adjacent channels may be added or added andaveraged to improve the S/N ratio of the dose signal DDS(C). Inaddition, the method which increases the number of gate lines 41 towhich the gate pulses G(R) are applied at the same time by the gatedriving unit 50 to increase the amount of charge added in each channeland the method which adds or adds and averages the dose signals DDS(C)between adjacent channels may be combined to improve the S/N ratio ofthe dose signal DDS(C).

The seventh invention may be combined with each embodiment of the firstinvention, the second invention, the third invention, and the fourthinvention. For example, as in the second to fourth inventions, the firstinvention may be applied such that the control unit 54 periodicallyswitches the power supply state of the ADC 77 and the MUX 76 which formthe block BL between the first state and the second state, asillustrated in FIG. 14 in the (1-1)-th embodiment.

As in the second and fourth inventions, the switching patterns of powersupply to the ADC 77 and the block BL in the seventh invention and thefirst invention may be combined as follows. First, in a case in whichthere are two or more blocks BL including the MUX 76 and the ADC 77whose power supply state is periodically switched as illustrated in, forexample, FIG. 14 of the (1-1)-th embodiment, the control unit 54 mayshift the switching timing of the power supply state of at least two ofthe two or more blocks BL.

In addition, the control unit 54 may shift the switching timing of thepower supply state for each of a plurality of groups to which two ormore blocks BL belong, as illustrated in, for example, FIG. 14 of the(1-1)-th embodiment. In this case, it is preferable that at least oneblock BL is disposed between two blocks BL belonging to the same group.Alternatively, as illustrated in, for example, FIG. 18 of the (1-2)-thembodiment, the switching timing of the power supply state of all of thetwo or more blocks BL may be shifted.

As illustrated in, for example, FIG. 21 of the (1-5)-th embodiment, in acase in which there are a plurality of blocks BL including the MUX 76 towhich only the non-detection CA 131 is connected, at least one of theplurality of blocks BL may be always in the second state.

As in the (1-12)-th embodiment illustrated in FIGS. 35 to 37, leakcharge correction and temperature drift correction may be performed forthe dose signal DDS(C).

In addition, the (1-8)-th embodiment illustrated in FIGS. 25 to 27 inwhich the detection channel 95 that is the signal line 42 to which thedetection pixel 90 used for the AED operation is connected is set, the(1-9)-th embodiment illustrated in FIGS. 28 to 31 in which the detectionpixel 90X used only for the AED operation is provided, the (1-10)-thembodiment illustrated in FIG. 32 in which the setting of the detectionpixel 90 can be changed, the (1-11)-th embodiment illustrated in FIGS.33 and 34 in which the operation of the CDS 61 in the AED operation issimplified, and the (1-13)-th embodiment illustrated in FIG. 38 in whichthe digital signal transmission I/F is switched may be combined witheach other.

Further, the (2-1)-th to (2-3)-th embodiments of the second inventionillustrated in FIGS. 39 to 43 may be applied to change at least one ofthe non-selected CAs other than some CAs that selectively output theanalog voltage signal V(C) to the ADC 77 to the power saving state inwhich power supplied to the non-selected CAs in the AED operation islower than normal power in the image reading operation.

In addition, the (3-1)-th and (3-2)-th embodiments illustrated in FIGS.44 to 49 in which the number of pulses per unit time in the clock signalof the ADC 77 is less than that in the image reading operation may beapplied.

Further, the (4-1)-th to (4-3)-th embodiments illustrated in FIGS. 50 to58 may be applied in which each of the plurality of blocks BL1 to BL16is switched from the second state to the first state a predeterminedtime, which is required to stably operate, for example, the ADC 77forming the block BL, before the start timing of charge reading in theAED operation.

In each embodiment of the first to seventh inventions, the electroniccassette 16 is given as an example of the radiographic image detectiondevice. However, the invention is not limited thereto. The invention canalso be applied to a stationary radiographic image detection device thatis fixed to the upright imaging table 18 or the decubitus imaging table19.

In each embodiment of the first to seventh inventions, for example, thefollowing various processors can be used as the hardware structure ofprocessing units performing various processes, such as the control unit54, the leak charge correction unit 121, and the temperature driftcorrection unit 122.

The various processors include, for example, a CPU, a programmable logicdevice (PLD), and a dedicated electric circuit. The CPU is ageneral-purpose processor that executes software (program) to functionas various processing units as is well known. The PLD is a processorsuch as a field programmable gate array (FPGA) whose circuitconfiguration can be changed after manufacture. The dedicated electriccircuit is a processor such as an application specific integratedcircuit (ASIC) which has a dedicated circuit configuration designed toperform a specific process.

One processing unit may be configured by one of the various processorsor a combination of two or more processors of the same type or differenttypes (for example, a combination of a plurality of FPGAs and acombination of a CPU and an FPGA). In addition, a plurality ofprocessing units may be configured by one processor. A first example ofthe configuration in which a plurality of processing units areconfigured by one processor is an aspect in which one processor isconfigured by a combination of one or more CPUs and software andfunctions as a plurality of processing units. A second example of theconfiguration is an aspect in which a processor that implements thefunctions of the entire system including a plurality of processing unitsusing one IC chip is used. A representative example of this aspect is asystem-on-chip (SoC). As such, various processing units are configuredby using one or more of the various processors as a hardware structure.

In addition, specifically, an electric circuit (circuitry) obtained bycombining circuit elements, such as semiconductor elements, is used asthe hardware structure of the various processors.

The invention is not limited to X-rays and can also be applied to a casein which other types of radiation including y-rays are used.

The conjunction “or” described in the specification is not an expressionintended to be a limited interpretation, such as any one of a pluralityof options connected by the conjunction, and is an expression includingcombinations of the plurality of options, depending on the context. Forexample, a sentence “an option A or an option B is performed” should beinterpreted as having the following three meanings, depending on thecontext: “the option A is performed”; “the option B is performed”; and“the option A and the option B are performed”.

The invention is not limited to each embodiment of the first to seventhinventions and may have various configurations as long as it does notdepart from the scope and spirit of the invention. In addition, theinvention may include a storage medium storing a program in addition tothe program.

EXPLANATION OF REFERENCES

-   10: X-ray imaging system-   11: X-ray generation apparatus-   12: X-ray imaging apparatus-   13: X-ray source-   14: radiation source control device-   15: irradiation switch-   16: electronic cassette (radiographic image detection device)-   17: console-   18: upright imaging table-   19: decubitus imaging table-   20: display-   21: input device-   22, 23: wireless communication unit-   25: menu and condition table-   30: sensor panel-   31: circuit unit-   32: housing-   32A: front surface-   33: transmission plate-   34: scintillator-   35: light detection substrate-   40: pixel-   41, 107: gate line-   42: signal line-   43, 105: photoelectric conversion unit-   44, 106: TFT-   50, 108: gate driving unit-   51: signal processing circuit-   52: memory-   53: power supply unit-   54: control unit-   60: charge amplifier (CA)-   61: correlated double sampling circuit (CDS)-   62: multiplexer (MUX) unit-   63: AD converter (ADC) unit-   65: battery-   66: wired communication unit-   70: operational amplifier-   71: capacitor-   72: amplifier reset switch-   73A: first sample-and-hold circuit (first S/H)-   73B: second sample-and-hold circuit (second S/H)-   74: difference amplifier-   75: (first to twelfth) gate driving circuit-   76, 76A, 76B, 135: (first to sixteenth) MUX-   77: (first to sixteenth) ADC-   90, 90X, 90X1 to 90X3: detection pixel-   95: detection channel-   100: short-circuit line-   120: reference channel-   121: leak charge correction unit-   122: temperature drift correction unit-   125: LVDS interface (I/F)-   126: CMOS interface (I/F)-   127: switch-   130: non-detection channel-   131: non-detection CA-   132: detection CA-   133: switch-   140, 200, 203: first path-   141, 201, 204: second path-   142, 202, 205, 206: switch-   207: bias power supply-   G(R): gate pulse-   V(C): analog voltage signal-   DS(C): digital signal-   DIS(C): image signal-   DDS(C): dose signal-   RCDDS(C): leak charge corrected dose signal-   DRCDDS(C): temperature drift corrected dose signal-   AR1 to AR16: area-   BL1 to BL16: block-   CP1 to CP4: chip-   T: unit time-   P_A, PON_A, PSL_A: power supplied to ADC-   ST100 to ST190, ST1202 to ST1206, ST1802 to ST1806, ST300 to ST330:    step-   LA1, LA2: area-   RLA1 to RLA3: range-   α(C): correction coefficient-   F {DRS(C−1), DRS(C+1)}: correction coefficient calculation formula-   TP: temperature of central portion of block-   SC: charge generated in detection pixel-   LC: leak charge-   P_C, PN_C, PL_C, PL_C1, PL_C2: power supplied to CA-   DT: alphabets indicating detection channel-   NDT: alphabets indicating non-detection channel-   NPU_A, NPUN_A, NPUL_A: pulse number per unit time in clock signal of    ADC-   CLN_A, CLL_A: clock signal of ADC-   TC: period of clock signal-   TW: time required to stably operate block-   TX: reading period of dose signal-   S_MUX, S_CA, S_CDS, S_BIAS: switch driving control signal

What is claimed is:
 1. A radiographic image detection device comprising:a sensor panel in which pixels that are sensitive to radiation which hasbeen emitted from a radiation generation apparatus and transmittedthrough a subject and accumulate charge are two-dimensionally arrangedand a plurality of signal lines for reading the charge are arranged; asignal processing circuit that reads an analog voltage signalcorresponding to the charge from the pixel through the signal line toperform signal processing; a plurality of charge amplifiers that areincluded in the signal processing circuit and each of which is providedfor each signal line, is connected to one end of the signal line, andconverts the charge from the pixel into the analog voltage signal; amultiplexer that is included in the signal processing circuit, has aplurality of input terminals to which the plurality of charge amplifiersare respectively connected, sequentially selects the analog voltagesignals from the plurality of charge amplifiers, and outputs theselected analog voltage signal; an AD converter that is included in thesignal processing circuit, is connected to a stage behind themultiplexer, and performs an AD conversion process of converting theanalog voltage signal output from the multiplexer into a digital signalcorresponding to a voltage value; and a processor configured to controlthe signal processing circuit such that an irradiation start detectionoperation and an image reading operation are performed, wherein theirradiation start detection operation reads the charge through adetection channel which is the signal line connected to a presetdetection pixel among the pixels from before start of the emission ofthe radiation and detects the start of the emission of the radiation onthe basis of the digital signal corresponding to the read charge, theimage reading operation reads the charge from the pixel through thesignal line after a pixel charge accumulation period for which thecharge is accumulated in the pixel elapses after the start of theemission of the radiation and outputs a radiographic image which isindicated by the digital signal corresponding to the read charge and isprovided for diagnosis, and in the irradiation start detectionoperation, the processor selectively outputs the analog voltage signalfrom a part of the charge amplifiers including a detection chargeamplifier that is the charge amplifier connected to the detectionchannel among the plurality of charge amplifiers connected to themultiplexer, to the AD converter, the processor causes the AD converterto perform only the AD conversion process for the analog voltage signalselectively output from the multiplexer, the processor further reducesthe number of pulses per unit time in a clock signal defining anoperation timing of the AD converter compared to that in the imagereading operation, and in the irradiation start detection operation, ina case where power supplied to the charge amplifier during the imagereading operation is normal power, the processor further drives at leastone of the part of charge amplifiers in a low power state in which powerlower than the normal power and greater than 0 is supplied.
 2. Theradiographic image detection device according to claim 1, wherein themultiplexer has a function of selecting the analog voltage signal fromthe part of the charge amplifiers among the plurality of chargeamplifiers connected thereto.
 3. The radiographic image detection deviceaccording to claim 1, further comprising: a first path through which theanalog voltage signal from the charge amplifier is output to the ADconverter via the multiplexer; a second path through which the analogvoltage signal from the charge amplifier is output to the AD converterwithout passing through the multiplexer; and a switch that selectivelyswitches between the first path and the second path, wherein theprocessor controls the switch to select the second path during theirradiation start detection operation.
 4. The radiographic imagedetection device according to claim 1, wherein in the irradiation startdetection operation, the processor causes at least one of non-selectedcharge amplifiers other than the part of the charge amplifiers among theplurality of charge amplifiers connected to the multiplexer to be in apower saving state in which the supply power is lower than the normalpower.
 5. The radiographic image detection device according to claim 4,wherein the power saving state is a low power state in which power lowerthan the normal power and greater than 0 is supplied.
 6. Theradiographic image detection device according to claim 4, wherein thepower saving state is a power-off state in which the supply of power isstopped.
 7. The radiographic image detection device according to claim4, wherein the processor causes all of the non-selected chargeamplifiers to be in the power saving state.
 8. The radiographic imagedetection device according to claim 4, further comprising: a first paththrough which the charge is input to the charge amplifier; a second paththrough which the charge is output to the multiplexer without passingthrough the charge amplifier; and a switch that selectively switchesbetween the first path and the second path, wherein the processorcontrols the switch to select the second path for the non-selectedcharge amplifier in the power saving state.
 9. The radiographic imagedetection device according to claim 8, wherein, in a case in which thepower saving state is a power-off state in which the supply of power isstopped, the processor applies a bias voltage for stabilizing apotential of an input stage to the non-selected charge amplifier in thepower-off state.
 10. The radiographic image detection device accordingto claim 1, further comprising: a plurality of blocks each of whichincludes one multiplexer to which at least one of the detection chargeamplifiers is connected and one AD converter connected to a stage behindthe one multiplexer, wherein the processor has a function of switching apower supply state of the block between a first state in which firstpower is supplied and a second state in which second power lower thanthe first power per unit time is supplied, and periodically switches thepower supply state of at least one of the plurality of blocks during theirradiation start detection operation.
 11. The radiographic imagedetection device according to claim 10, wherein in a case where thenumber of blocks whose power supply state is periodically switched istwo or more, the control unit shifts a switching timing of the powersupply state of at least two of the two or more blocks.
 12. Theradiographic image detection device according to claim 11, wherein thetwo or more blocks are divided into groups, and the processor shifts theswitching timing of the power supply state for each group.
 13. Theradiographic image detection device according to claim 12, wherein atleast one block is disposed between two blocks belonging to the samegroup.
 14. The radiographic image detection device according to claim11, wherein the processor shifts the switching timing of the powersupply state of all of the two or more blocks.
 15. The radiographicimage detection device according to claim 10, wherein the processorcauses at least one of the blocks including the multiplexer to which thepart of charge amplifiers is not connected to be in the second state atall the times among the plurality of blocks during the irradiation startdetection operation.
 16. The radiographic image detection deviceaccording to claim 10, wherein the block is provided for each area thatis formed by the pixels connected to a plurality of the adjacent signallines.
 17. The radiographic image detection device according to claim16, wherein a plurality of the adjacent blocks that are in charge of theareas adjacent to each other are mounted on the same chip, and aplurality of the chips are provided.
 18. The radiographic imagedetection device according to claim 17, wherein the processor switchesthe power supply state of the block in units of the blocks that are incharge of the areas or in units of the chips.
 19. The radiographic imagedetection device according to claim 1, wherein the processor corrects atemperature drift of the digital signal which is generated by a bias ina temperature distribution in the signal processing circuit due to theswitching of the power supply state of the block.
 20. A method foroperating a radiographic image detection device comprising a sensorpanel in which pixels that are sensitive to radiation which has beenemitted from a radiation generation apparatus and transmitted through asubject and accumulate charge are two-dimensionally arranged and aplurality of signal lines for reading the charge are arranged, a signalprocessing circuit that reads an analog voltage signal corresponding tothe charge from the pixel through the signal line to perform signalprocessing, a plurality of charge amplifiers that are included in thesignal processing circuit and each of which is provided for each signalline, is connected to one end of the signal line, and converts thecharge from the pixel into the analog voltage signal, a multiplexer thatis included in the signal processing circuit, has a plurality of inputterminals to which the plurality of charge amplifiers are respectivelyconnected, sequentially selects the analog voltage signals from theplurality of charge amplifiers, and outputs the selected analog voltagesignal, an AD converter that is included in the signal processingcircuit, is connected to a stage behind the multiplexer, and performs anAD conversion process of converting the analog voltage signal outputfrom the multiplexer into a digital signal corresponding to a voltagevalue, and a processor configured to control the signal processingcircuit such that an irradiation start detection operation and an imagereading operation are performed, the method comprising: an irradiationstart detection step of performing an irradiation start detectionoperation that reads the charge through a detection channel which is thesignal line connected to a preset detection pixel among the pixels frombefore start of the emission of the radiation and detects the start ofthe emission of the radiation on the basis of the digital signalcorresponding to the read charge; and an image reading step ofperforming an image reading operation that reads the charge from thepixel through the signal line after a pixel charge accumulation periodfor which the charge is accumulated in the pixel elapses from the startof the emission of the radiation and outputs a radiographic image whichis indicated by the digital signal corresponding to the read charge andis provided for diagnosis, wherein in the irradiation start detectionstep, the analog voltage signal from a part of the charge amplifiersincluding a detection charge amplifier that is the charge amplifierconnected to the detection channel among the plurality of chargeamplifiers connected to the multiplexer is selectively output to the ADconverter, the AD converter is caused to perform only the AD conversionprocess for the analog voltage signal output from the multiplexer, thenumber of pulses per unit time in a clock signal defining an operationtiming of the AD converter is further reduced compared to that in theimage reading operation, and in the irradiation start detectionoperation, in a case where power supplied to the charge amplifier duringthe image reading operation is normal power, at least one of the part ofcharge amplifiers is further driven in a low power state in which powerlower than the normal power and greater than 0 is supplied.